Tom Letowski - Academia.edu (original) (raw)

Papers by Tom Letowski

Research paper thumbnail of Bone Conduction Communication: Research Progress and Directions

: This report is a follow-on report to previous US Army Research Laboratory (ARL) work that serve... more : This report is a follow-on report to previous US Army Research Laboratory (ARL) work that served as a summary of bone conduction research that had been conducted to 2007 and provided a foundation for future research studies. Since then several more bone conduction communication studies both external and by ARL have been conducted to investigate the various characteristics of bone conduction communication systems. Progress has been made in understanding the nature of bone conduction hearing and speech perception, bone conduction psychophysics, and bone conduction technology. A number of bone conduction devices have been developed around the world, mostly outside of the United States; however, state-of-the-art bone conduction systems and bone conduction literature are not easily available due to their commercial limitations, trade restrictions, and military applications. However, there is still a scarcity of information about bone conduction in open literature and in trade magazines...

Research paper thumbnail of Measuring directional masking in a sound field using adaptive threshold procedures

Archives of Acoustics, 2014

The accuracy of three adaptive threshold procedures for measuring directional masking was assesse... more The accuracy of three adaptive threshold procedures for measuring directional masking was assessed in two experiments. For each experiment, detection of a target signal, located at either 0$^{\circ}$, 90$^{\circ}$, 180$^{\circ}$ or 270$^{\circ}$ azimuth was measured in the presence of a masker located at 0$^{\circ}$, 90$^{\circ}$ or 180$^{\circ}$ azimuth. In Experiment 1, masked thresholds for ten normal hearing subjects were measured using the Bekesy Procedure and an Ascending Up-and-Down Procedure. In Experiment 2, masked thresholds for another group of ten normal hearing subjects were measured using the Bekesy Procedure and a Maximum Likelihood Procedure. Results confirmed the dependence of detection thresholds on the angular separation between the target and masker. In addition, threshold reliability depended on the location of the signal and the masker. No statistically significant differences were found in detection thresholds over repeated trials or between threshold procedur...

Research paper thumbnail of Detection and recognition of natural sounds

Archives of Acoustics, 2007

Human-machine interfaces and environment simulators increasingly depend on audio interfaces. Acou... more Human-machine interfaces and environment simulators increasingly depend on audio interfaces. Acoustic signals are used to provide warnings, feedback, information about the state of a system, and to enhance the immersive character of virtual reality environments. In order to decrease the mental workload of the listener, increase the speed of interaction, and minimize the chances for operational error, the audio signals (auditory icons) should have a natural character and clearly differ in their spatial, spectral, and temporal characteristics. Therefore, the design and selection of audio signals for specific applications should be based on the detectability and recognizability of the signals in the intended environments and on the meaningful connotations of the individual sounds. The present study was conducted to assess the detection and recognition thresholds of 30 pre-selected sounds and to determine the specific acoustic properties that make complex natural sounds effective audito...

Research paper thumbnail of Timbre, tone color, and sound quality: concepts and definitions

Archives of Acoustics, May 1, 2014

Research paper thumbnail of Assessment of frequency selectivity with psychoacoustic masking curves

Archives of Acoustics, 2014

Research paper thumbnail of Bone Conduction Communication: Research Progress and Directions

Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),

Research paper thumbnail of Induction loop listening system designed for a classroom

PubMed, 1986

The principles of designing an induction loop listening system are discussed. Step-by-step proced... more The principles of designing an induction loop listening system are discussed. Step-by-step procedures for building an induction loop are presented. The loop described was installed in a medium-size classroom and listening tests were performed comparing the loop and loudspeakers. Two groups of hearing impaired listeners were used. One group of listeners wore hearing aids while the other group did not. Result indicated that for both groups, speech perception was enhanced with the loop system.

Research paper thumbnail of Word discrimination in various multitalker noises

The Journal of the Acoustical Society of America, 1993

A large number of different multitalker noises (MTNs) is used in research and clinical applicatio... more A large number of different multitalker noises (MTNs) is used in research and clinical applications. These noises differ in acoustical, semantic, and linguistic properties and, thus, may have different masking effectiveness. The authors compared acoustical characteristics and masking effectiveness of several MTNs recorded by the authors and by others. Both spectral and temporal differences have been observed among various MTNs. When noises of similar acoustic characteristics have been compared, the gender of the talkers but not the speech material affected masking effectiveness of the MTN.

Research paper thumbnail of Listening systems—Application analysis

The Journal of the Acoustical Society of America, 1982

For many years, listening systems have been used for the hearing-impaireds in schools for the dea... more For many years, listening systems have been used for the hearing-impaireds in schools for the deaf and the general public for simultaneous transmission in several languages. Recently, listening systems started to be installed for pleasure listening in theaters, churches and concert halls. For multi-lingual conferences, the main emphasis was on separation of the channels. This is usually achieved by hard-wired connections with limited frequency response to the range most important for speech intelligibility. The systems for the hard-of-hearing have also limited frequency response, a philosophy inherited from hearing aids. The priority here was adequate gain allowed by the system, provision to couple with personal hearing aids, and sometimes flexibility in seat selection. The modern listening systems installed in public places should serve both the general public and hard-of-hearing listeners. They are designed for both speech and music transmission and quality of sound becomes the pr...

Research paper thumbnail of Spatial audiometry: detection of spondaic words in noise

Journal of the American Academy of Audiology, 1998

It is important to select appropriate stimuli and test conditions for developing standardized spa... more It is important to select appropriate stimuli and test conditions for developing standardized spatial audiometric tests. In three experiments, binaural detection thresholds (BDTs) for a target signal, located at either 0, 45, 90, 135, 180, 225, 270, or 315 degrees azimuth, were measured in the presence of a masker positioned at one of these eight locations. Target signals included spondaic words from the CID W-1 list. The masker was speech spectrum noise (SSN) or multitalker noise (MTN) presented at a constant level (65 dBA). Bekesy tracking was used to measure BDTs in listeners with normal hearing. Results indicate that BDTs are significantly influenced by the (a) angular separation between the target and noise source and (b) choice of spondaic words used as target stimuli. BDTs for various spondaic words differed as much as 13 dB for a given angular separation. BDTs measured in SSN and MTN for otherwise identical test conditions differed less than 3 dB. A single spondaic word appe...

Research paper thumbnail of Spatial audiometry: detection of spondaic words in noise

PubMed, Dec 1, 1998

It is important to select appropriate stimuli and test conditions for developing standardized spa... more It is important to select appropriate stimuli and test conditions for developing standardized spatial audiometric tests. In three experiments, binaural detection thresholds (BDTs) for a target signal, located at either 0, 45, 90, 135, 180, 225, 270, or 315 degrees azimuth, were measured in the presence of a masker positioned at one of these eight locations. Target signals included spondaic words from the CID W-1 list. The masker was speech spectrum noise (SSN) or multitalker noise (MTN) presented at a constant level (65 dBA). Bekesy tracking was used to measure BDTs in listeners with normal hearing. Results indicate that BDTs are significantly influenced by the (a) angular separation between the target and noise source and (b) choice of spondaic words used as target stimuli. BDTs for various spondaic words differed as much as 13 dB for a given angular separation. BDTs measured in SSN and MTN for otherwise identical test conditions differed less than 3 dB. A single spondaic word appears to be appropriate for spatial audiometric tests of detection. Nonsignificant differences between masked BDTs obtained for SSN and MTN noises indicate that for spatial detection, the masking effects of these noises are comparable. These results indicate that the development of a clinical test of spatial detection should include the use of SSN and a single spondaic word, with detection being measured for a set of four or five signal and noise source configurations.

Research paper thumbnail of A Procedure for Measuring Speech Detection in Directional Noise

Noise-Con 04. The 2004 National Conference on Noise Control EngineeringInstitute of Noise Control EngineeringTransportation Research Board, 2004

This paper examined the use of the Bekesy tracking technique for the measuring of directional det... more This paper examined the use of the Bekesy tracking technique for the measuring of directional detection thresholds in noise, in various speech and noise loudspeaker configurations. The tracking technique appears to hold promise as a method for measuring speech thresholds quickly and accurately. Further, the results of this study provide the information necessary to select a subset of loudspeaker configurations that would adequately reflect a listener’s ability to detect speech in directional or nondirectional noise as well as provide the reference data that could be used to establish the normative thresholds. The test should be completed in about 5-6 minutes using suggested configurations.

Research paper thumbnail of An Influence of Binaural Hearing Aids on Positioning of Sound Images

Journal of Speech Language and Hearing Research, Sep 1, 1980

An influence of binaural hearing aids on positioning of sound images produced by signals from two... more An influence of binaural hearing aids on positioning of sound images produced by signals from two loudspeakers was investigated with normally hearing and hearing-impaired subjects. The image can be positioned along a horizontal line connecting the centers of the sources by adjusting the relative sound pressure levels of signals. When the listener is a symmetrical receiver, the image appears on the midline (0 degrees azimuth) for equal levels or away from the midline for unequal levels. Any asymmetry of the receiver causes a shift of the image away from the midline. In the study, the level differences, delta Ls, necessary to position sound images at 0 and +/- 12 degrees azimuths were measured. The baseline data were collected for 10 normally hearing subjects in unaided and aided conditions. In the aided conditions binaural aids were balanced (equal gains) or unbalanced (10 dB disparity in gains). The normally hearing subjects positioned the image on the midline with a group mean delta L of 0 dB in both unaided and balanced aided conditions. To position the image at +12 or -12 degrees azimuth they needed mean delta Ls that could be predicted from a theoretical equation. With unbalanced aids, a group mean delta L of +3 or -3 dB was needed for the midline image. The delta Ls for the side images also were shifted. For 12 hearing-impaired subjects with bilateral lossses, the midline delta Ls in unaided condition were within the normal range (+/- 2 dB). For two monaural hearing aid users with long experience, the midline delta Ls were greater than normal. The delta Ls for the side images were equal to or greatr than delta Ls for normally hearing subjects. In aided balanced and/or unbalanced conditions, some hearing-impaired subjects needed delta Ls for the midline image outside the normal range, and some could not position the image at the side azimuths. It was concluded that the binaural hearing aids can be a source of receiver asymmetry.

Research paper thumbnail of Understanding of time-compressed speech by older adults: effect of discard interval

PubMed, Nov 1, 1995

Fifteen subjects, aged 60 to 74 years, participated in a study to assess the role of discard inte... more Fifteen subjects, aged 60 to 74 years, participated in a study to assess the role of discard interval (DI) length in the understanding of time-compressed connected speech by older adults. The subjects' task was to report associations among the items mentioned in a passage. Results indicate that performance deteriorated gradually until a critical DI of 75 msec was reached, beyond which performance dropped sharply. Results should help in the better understanding of speech perception by older listeners and may be useful in development of a standardized test for evaluating speech understanding in older individuals whose auditory complaints are often not explained by their peripheral hearing loss.

Research paper thumbnail of Comprehension of time-compressed speech: effects of age and speech complexity

PubMed, Dec 1, 1996

The periodic sampling method of time compression is characterized by periodic removal of segments... more The periodic sampling method of time compression is characterized by periodic removal of segments of speech according to predetermined compression rate (CR) and discard interval length (DIL). Fifteen middle-aged (42-54 years old) and 15 older (60-69 years old) adults participated in the study that assessed the combined effects of CR and DIL on the comprehension of time-compressed speech by aging adults. Three CRs (30, 45, and 60%), seven DILs (35 through 155 msec), and two types of speech materials were used. The subject's task was to report associations among the items mentioned in a time-compressed passage. In all cases, performance of the subjects deteriorated with increasing CR and DIL. The older adults were affected more by CR and DIL values than middle-aged adults. The difference in sentence complexity between the two speech materials affected both groups equally. In general, the results of the study indicated that (a) time-compressed speech differentiates between speech comprehension by middle-aged and older adults and (b) the effects of CR and DIL became more independent with increasing age of the listener and increasing complexity of the speech material. Reported results support the concept that time-compressed speech may be an effective signal in clinical assessment of adults whose auditory complaints are not explained by their peripheral hearing losses.

Research paper thumbnail of Toleration of background noises: relationship with patterns of hearing aid use by elderly persons

PubMed, Jun 1, 1991

One of the frequently quoted reasons for the rejection of hearing aids is amplification of backgr... more One of the frequently quoted reasons for the rejection of hearing aids is amplification of background noise. The relationship between hearing aid use and toleration of background noise was assessed. Four groups of elderly subjects (at least 65 years old) and one group of young subjects with normal hearing participated in the study. Each group consisted of 15 subjects. The young subjects and elderly subjects in one group with relatively good hearing were tested for comparison with the hearing-impaired subjects. Elderly subjects in the three remaining groups had acquired hearing losses and had been fitted with hearing aids. The subjects were assigned to three groups on the basis of hearing aid use: full-time users, part-time users, and nonusers. The amount of background noise tolerated when listening to speech was tested. The speech stimulus was a story read by a woman and set at an individually chosen most comfortable level. The maskers were a babble of voices, speech-spectrum noise, traffic noise, music, and the noise of a pneumatic drill. There was a significant interaction between groups and noises. The full-time users tolerated significantly higher levels of music and speech-spectrum noise than part-time users and nonusers. In addition, the full-time users, but not the part-time users, assessed themselves as less handicapped in everyday functions when they wore hearing aids than when they did not wear their hearing aids.

Research paper thumbnail of Analysis of Subjective Measurement Methods of Transmission Characteristics of Earphones

Research paper thumbnail of Detection and recognition of natural sounds

Archives of Acoustics, 2007

Human-machine interfaces and environment simulators increasingly depend on audio interfaces. Acou... more Human-machine interfaces and environment simulators increasingly depend on audio interfaces. Acoustic signals are used to provide warnings, feedback, information about the state of a system, and to enhance the immersive character of virtual reality environments. In order to decrease the mental workload of the listener, increase the speed of interaction, and minimize the chances for operational error, the audio signals (auditory icons) should have a natural character and clearly differ in their spatial, spectral, and temporal characteristics. Therefore, the design and selection of audio signals for specific applications should be based on the detectability and recognizability of the signals in the intended environments and on the meaningful connotations of the individual sounds. The present study was conducted to assess the detection and recognition thresholds of 30 pre-selected sounds and to determine the specific acoustic properties that make complex natural sounds effective auditory icons. The results of the study revealed a strong dependence of both types of threshold on the type of sound and a relative independence of both thresholds. The sound level difference between the detection and recognition thresholds varied from 1 to 13 dB and should be considered as an important criterion in auditory icon selection.

Research paper thumbnail of Most Comfortable Listening Level and Speech Attenuation by Hearing Protectors

International Journal of Occupational Safety and Ergonomics, 1995

H earing protectors atte n u ate both th e background noise and th e useful sounds e m b e d ded ... more H earing protectors atte n u ate both th e background noise and th e useful sounds e m b e d ded in noise such as th e sounds o f speech and w arn in g signals. An effective hearing p ro tecto r is o ne th a t attenu ates background noise w h ile leaving su fficien t en erg y of speech and w arn in g signals to reach th e ear of th e w orker. A t present, h ow ever, th ere are no established criteria fo r assessing effective ch an g e in sp eech-ton o ise ratio caused by hearing protection devices (HPDs). O ne such criterion could be a ch an g e in m o st c o m fo rta b le (listening) level (M CL) fo r speech caused by th e presence of HPDs. In this stu d y th e H P D-related shift in M C L fo r speech presented in q uiet w a s m easu red and co m p ared w ith tw o m easures of noise attenu atio n: N oise Reduction Rating (NRR) and h ig h-m e d iu m-lo w (H-M-L). T h e results indicate th at the M C L shift m a y be a sensitive m easure o f speech attenu atio n by HPDs, w hich to g e th e r w ith th e ap p ro p ria te H-M-L m a y describe technical p ro perties of HPDs. hearing protection m ost c o m fo rta b le level speech perception

Research paper thumbnail of Comparative Analysis of Microphone Recordings Registered at Various Points of the Vocal Tract

Folia Phoniatrica Et Logopaedica, 1972

Research paper thumbnail of Bone Conduction Communication: Research Progress and Directions

: This report is a follow-on report to previous US Army Research Laboratory (ARL) work that serve... more : This report is a follow-on report to previous US Army Research Laboratory (ARL) work that served as a summary of bone conduction research that had been conducted to 2007 and provided a foundation for future research studies. Since then several more bone conduction communication studies both external and by ARL have been conducted to investigate the various characteristics of bone conduction communication systems. Progress has been made in understanding the nature of bone conduction hearing and speech perception, bone conduction psychophysics, and bone conduction technology. A number of bone conduction devices have been developed around the world, mostly outside of the United States; however, state-of-the-art bone conduction systems and bone conduction literature are not easily available due to their commercial limitations, trade restrictions, and military applications. However, there is still a scarcity of information about bone conduction in open literature and in trade magazines...

Research paper thumbnail of Measuring directional masking in a sound field using adaptive threshold procedures

Archives of Acoustics, 2014

The accuracy of three adaptive threshold procedures for measuring directional masking was assesse... more The accuracy of three adaptive threshold procedures for measuring directional masking was assessed in two experiments. For each experiment, detection of a target signal, located at either 0$^{\circ}$, 90$^{\circ}$, 180$^{\circ}$ or 270$^{\circ}$ azimuth was measured in the presence of a masker located at 0$^{\circ}$, 90$^{\circ}$ or 180$^{\circ}$ azimuth. In Experiment 1, masked thresholds for ten normal hearing subjects were measured using the Bekesy Procedure and an Ascending Up-and-Down Procedure. In Experiment 2, masked thresholds for another group of ten normal hearing subjects were measured using the Bekesy Procedure and a Maximum Likelihood Procedure. Results confirmed the dependence of detection thresholds on the angular separation between the target and masker. In addition, threshold reliability depended on the location of the signal and the masker. No statistically significant differences were found in detection thresholds over repeated trials or between threshold procedur...

Research paper thumbnail of Detection and recognition of natural sounds

Archives of Acoustics, 2007

Human-machine interfaces and environment simulators increasingly depend on audio interfaces. Acou... more Human-machine interfaces and environment simulators increasingly depend on audio interfaces. Acoustic signals are used to provide warnings, feedback, information about the state of a system, and to enhance the immersive character of virtual reality environments. In order to decrease the mental workload of the listener, increase the speed of interaction, and minimize the chances for operational error, the audio signals (auditory icons) should have a natural character and clearly differ in their spatial, spectral, and temporal characteristics. Therefore, the design and selection of audio signals for specific applications should be based on the detectability and recognizability of the signals in the intended environments and on the meaningful connotations of the individual sounds. The present study was conducted to assess the detection and recognition thresholds of 30 pre-selected sounds and to determine the specific acoustic properties that make complex natural sounds effective audito...

Research paper thumbnail of Timbre, tone color, and sound quality: concepts and definitions

Archives of Acoustics, May 1, 2014

Research paper thumbnail of Assessment of frequency selectivity with psychoacoustic masking curves

Archives of Acoustics, 2014

Research paper thumbnail of Bone Conduction Communication: Research Progress and Directions

Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),

Research paper thumbnail of Induction loop listening system designed for a classroom

PubMed, 1986

The principles of designing an induction loop listening system are discussed. Step-by-step proced... more The principles of designing an induction loop listening system are discussed. Step-by-step procedures for building an induction loop are presented. The loop described was installed in a medium-size classroom and listening tests were performed comparing the loop and loudspeakers. Two groups of hearing impaired listeners were used. One group of listeners wore hearing aids while the other group did not. Result indicated that for both groups, speech perception was enhanced with the loop system.

Research paper thumbnail of Word discrimination in various multitalker noises

The Journal of the Acoustical Society of America, 1993

A large number of different multitalker noises (MTNs) is used in research and clinical applicatio... more A large number of different multitalker noises (MTNs) is used in research and clinical applications. These noises differ in acoustical, semantic, and linguistic properties and, thus, may have different masking effectiveness. The authors compared acoustical characteristics and masking effectiveness of several MTNs recorded by the authors and by others. Both spectral and temporal differences have been observed among various MTNs. When noises of similar acoustic characteristics have been compared, the gender of the talkers but not the speech material affected masking effectiveness of the MTN.

Research paper thumbnail of Listening systems—Application analysis

The Journal of the Acoustical Society of America, 1982

For many years, listening systems have been used for the hearing-impaireds in schools for the dea... more For many years, listening systems have been used for the hearing-impaireds in schools for the deaf and the general public for simultaneous transmission in several languages. Recently, listening systems started to be installed for pleasure listening in theaters, churches and concert halls. For multi-lingual conferences, the main emphasis was on separation of the channels. This is usually achieved by hard-wired connections with limited frequency response to the range most important for speech intelligibility. The systems for the hard-of-hearing have also limited frequency response, a philosophy inherited from hearing aids. The priority here was adequate gain allowed by the system, provision to couple with personal hearing aids, and sometimes flexibility in seat selection. The modern listening systems installed in public places should serve both the general public and hard-of-hearing listeners. They are designed for both speech and music transmission and quality of sound becomes the pr...

Research paper thumbnail of Spatial audiometry: detection of spondaic words in noise

Journal of the American Academy of Audiology, 1998

It is important to select appropriate stimuli and test conditions for developing standardized spa... more It is important to select appropriate stimuli and test conditions for developing standardized spatial audiometric tests. In three experiments, binaural detection thresholds (BDTs) for a target signal, located at either 0, 45, 90, 135, 180, 225, 270, or 315 degrees azimuth, were measured in the presence of a masker positioned at one of these eight locations. Target signals included spondaic words from the CID W-1 list. The masker was speech spectrum noise (SSN) or multitalker noise (MTN) presented at a constant level (65 dBA). Bekesy tracking was used to measure BDTs in listeners with normal hearing. Results indicate that BDTs are significantly influenced by the (a) angular separation between the target and noise source and (b) choice of spondaic words used as target stimuli. BDTs for various spondaic words differed as much as 13 dB for a given angular separation. BDTs measured in SSN and MTN for otherwise identical test conditions differed less than 3 dB. A single spondaic word appe...

Research paper thumbnail of Spatial audiometry: detection of spondaic words in noise

PubMed, Dec 1, 1998

It is important to select appropriate stimuli and test conditions for developing standardized spa... more It is important to select appropriate stimuli and test conditions for developing standardized spatial audiometric tests. In three experiments, binaural detection thresholds (BDTs) for a target signal, located at either 0, 45, 90, 135, 180, 225, 270, or 315 degrees azimuth, were measured in the presence of a masker positioned at one of these eight locations. Target signals included spondaic words from the CID W-1 list. The masker was speech spectrum noise (SSN) or multitalker noise (MTN) presented at a constant level (65 dBA). Bekesy tracking was used to measure BDTs in listeners with normal hearing. Results indicate that BDTs are significantly influenced by the (a) angular separation between the target and noise source and (b) choice of spondaic words used as target stimuli. BDTs for various spondaic words differed as much as 13 dB for a given angular separation. BDTs measured in SSN and MTN for otherwise identical test conditions differed less than 3 dB. A single spondaic word appears to be appropriate for spatial audiometric tests of detection. Nonsignificant differences between masked BDTs obtained for SSN and MTN noises indicate that for spatial detection, the masking effects of these noises are comparable. These results indicate that the development of a clinical test of spatial detection should include the use of SSN and a single spondaic word, with detection being measured for a set of four or five signal and noise source configurations.

Research paper thumbnail of A Procedure for Measuring Speech Detection in Directional Noise

Noise-Con 04. The 2004 National Conference on Noise Control EngineeringInstitute of Noise Control EngineeringTransportation Research Board, 2004

This paper examined the use of the Bekesy tracking technique for the measuring of directional det... more This paper examined the use of the Bekesy tracking technique for the measuring of directional detection thresholds in noise, in various speech and noise loudspeaker configurations. The tracking technique appears to hold promise as a method for measuring speech thresholds quickly and accurately. Further, the results of this study provide the information necessary to select a subset of loudspeaker configurations that would adequately reflect a listener’s ability to detect speech in directional or nondirectional noise as well as provide the reference data that could be used to establish the normative thresholds. The test should be completed in about 5-6 minutes using suggested configurations.

Research paper thumbnail of An Influence of Binaural Hearing Aids on Positioning of Sound Images

Journal of Speech Language and Hearing Research, Sep 1, 1980

An influence of binaural hearing aids on positioning of sound images produced by signals from two... more An influence of binaural hearing aids on positioning of sound images produced by signals from two loudspeakers was investigated with normally hearing and hearing-impaired subjects. The image can be positioned along a horizontal line connecting the centers of the sources by adjusting the relative sound pressure levels of signals. When the listener is a symmetrical receiver, the image appears on the midline (0 degrees azimuth) for equal levels or away from the midline for unequal levels. Any asymmetry of the receiver causes a shift of the image away from the midline. In the study, the level differences, delta Ls, necessary to position sound images at 0 and +/- 12 degrees azimuths were measured. The baseline data were collected for 10 normally hearing subjects in unaided and aided conditions. In the aided conditions binaural aids were balanced (equal gains) or unbalanced (10 dB disparity in gains). The normally hearing subjects positioned the image on the midline with a group mean delta L of 0 dB in both unaided and balanced aided conditions. To position the image at +12 or -12 degrees azimuth they needed mean delta Ls that could be predicted from a theoretical equation. With unbalanced aids, a group mean delta L of +3 or -3 dB was needed for the midline image. The delta Ls for the side images also were shifted. For 12 hearing-impaired subjects with bilateral lossses, the midline delta Ls in unaided condition were within the normal range (+/- 2 dB). For two monaural hearing aid users with long experience, the midline delta Ls were greater than normal. The delta Ls for the side images were equal to or greatr than delta Ls for normally hearing subjects. In aided balanced and/or unbalanced conditions, some hearing-impaired subjects needed delta Ls for the midline image outside the normal range, and some could not position the image at the side azimuths. It was concluded that the binaural hearing aids can be a source of receiver asymmetry.

Research paper thumbnail of Understanding of time-compressed speech by older adults: effect of discard interval

PubMed, Nov 1, 1995

Fifteen subjects, aged 60 to 74 years, participated in a study to assess the role of discard inte... more Fifteen subjects, aged 60 to 74 years, participated in a study to assess the role of discard interval (DI) length in the understanding of time-compressed connected speech by older adults. The subjects' task was to report associations among the items mentioned in a passage. Results indicate that performance deteriorated gradually until a critical DI of 75 msec was reached, beyond which performance dropped sharply. Results should help in the better understanding of speech perception by older listeners and may be useful in development of a standardized test for evaluating speech understanding in older individuals whose auditory complaints are often not explained by their peripheral hearing loss.

Research paper thumbnail of Comprehension of time-compressed speech: effects of age and speech complexity

PubMed, Dec 1, 1996

The periodic sampling method of time compression is characterized by periodic removal of segments... more The periodic sampling method of time compression is characterized by periodic removal of segments of speech according to predetermined compression rate (CR) and discard interval length (DIL). Fifteen middle-aged (42-54 years old) and 15 older (60-69 years old) adults participated in the study that assessed the combined effects of CR and DIL on the comprehension of time-compressed speech by aging adults. Three CRs (30, 45, and 60%), seven DILs (35 through 155 msec), and two types of speech materials were used. The subject's task was to report associations among the items mentioned in a time-compressed passage. In all cases, performance of the subjects deteriorated with increasing CR and DIL. The older adults were affected more by CR and DIL values than middle-aged adults. The difference in sentence complexity between the two speech materials affected both groups equally. In general, the results of the study indicated that (a) time-compressed speech differentiates between speech comprehension by middle-aged and older adults and (b) the effects of CR and DIL became more independent with increasing age of the listener and increasing complexity of the speech material. Reported results support the concept that time-compressed speech may be an effective signal in clinical assessment of adults whose auditory complaints are not explained by their peripheral hearing losses.

Research paper thumbnail of Toleration of background noises: relationship with patterns of hearing aid use by elderly persons

PubMed, Jun 1, 1991

One of the frequently quoted reasons for the rejection of hearing aids is amplification of backgr... more One of the frequently quoted reasons for the rejection of hearing aids is amplification of background noise. The relationship between hearing aid use and toleration of background noise was assessed. Four groups of elderly subjects (at least 65 years old) and one group of young subjects with normal hearing participated in the study. Each group consisted of 15 subjects. The young subjects and elderly subjects in one group with relatively good hearing were tested for comparison with the hearing-impaired subjects. Elderly subjects in the three remaining groups had acquired hearing losses and had been fitted with hearing aids. The subjects were assigned to three groups on the basis of hearing aid use: full-time users, part-time users, and nonusers. The amount of background noise tolerated when listening to speech was tested. The speech stimulus was a story read by a woman and set at an individually chosen most comfortable level. The maskers were a babble of voices, speech-spectrum noise, traffic noise, music, and the noise of a pneumatic drill. There was a significant interaction between groups and noises. The full-time users tolerated significantly higher levels of music and speech-spectrum noise than part-time users and nonusers. In addition, the full-time users, but not the part-time users, assessed themselves as less handicapped in everyday functions when they wore hearing aids than when they did not wear their hearing aids.

Research paper thumbnail of Analysis of Subjective Measurement Methods of Transmission Characteristics of Earphones

Research paper thumbnail of Detection and recognition of natural sounds

Archives of Acoustics, 2007

Human-machine interfaces and environment simulators increasingly depend on audio interfaces. Acou... more Human-machine interfaces and environment simulators increasingly depend on audio interfaces. Acoustic signals are used to provide warnings, feedback, information about the state of a system, and to enhance the immersive character of virtual reality environments. In order to decrease the mental workload of the listener, increase the speed of interaction, and minimize the chances for operational error, the audio signals (auditory icons) should have a natural character and clearly differ in their spatial, spectral, and temporal characteristics. Therefore, the design and selection of audio signals for specific applications should be based on the detectability and recognizability of the signals in the intended environments and on the meaningful connotations of the individual sounds. The present study was conducted to assess the detection and recognition thresholds of 30 pre-selected sounds and to determine the specific acoustic properties that make complex natural sounds effective auditory icons. The results of the study revealed a strong dependence of both types of threshold on the type of sound and a relative independence of both thresholds. The sound level difference between the detection and recognition thresholds varied from 1 to 13 dB and should be considered as an important criterion in auditory icon selection.

Research paper thumbnail of Most Comfortable Listening Level and Speech Attenuation by Hearing Protectors

International Journal of Occupational Safety and Ergonomics, 1995

H earing protectors atte n u ate both th e background noise and th e useful sounds e m b e d ded ... more H earing protectors atte n u ate both th e background noise and th e useful sounds e m b e d ded in noise such as th e sounds o f speech and w arn in g signals. An effective hearing p ro tecto r is o ne th a t attenu ates background noise w h ile leaving su fficien t en erg y of speech and w arn in g signals to reach th e ear of th e w orker. A t present, h ow ever, th ere are no established criteria fo r assessing effective ch an g e in sp eech-ton o ise ratio caused by hearing protection devices (HPDs). O ne such criterion could be a ch an g e in m o st c o m fo rta b le (listening) level (M CL) fo r speech caused by th e presence of HPDs. In this stu d y th e H P D-related shift in M C L fo r speech presented in q uiet w a s m easu red and co m p ared w ith tw o m easures of noise attenu atio n: N oise Reduction Rating (NRR) and h ig h-m e d iu m-lo w (H-M-L). T h e results indicate th at the M C L shift m a y be a sensitive m easure o f speech attenu atio n by HPDs, w hich to g e th e r w ith th e ap p ro p ria te H-M-L m a y describe technical p ro perties of HPDs. hearing protection m ost c o m fo rta b le level speech perception

Research paper thumbnail of Comparative Analysis of Microphone Recordings Registered at Various Points of the Vocal Tract

Folia Phoniatrica Et Logopaedica, 1972