Paul Reinhart

Songlike vocalizations from the Sumatran Rhinoceros (Dicerorhinus sumatrensis)

There are only 200 to 300 Sumatran rhinos (Dicermoceros sumatrensis) left in the world. Sumatran rhinos are solitary, and their native habitat is dense tropical forest and mountain moss forest. Three Sumatran rhinos, housed at the Cincinnati Zoo, were recorded using Statham Radio microphones and Sony TCD-D8 DAT recorders. Sumatran rhinos produce sounds described as eeps, 70 Hz–4 kHz (57–92 dB); whales, 100 Hz–3.2 kHz (87 dB); and whistle-blows, 17 Hz–8 kHz (100 dB). The whistle-blows contain high level infrasound that would be advantageous for use in the rhino’s forest habitat. Some Sumatran rhino vocalizations resemble humpback whale signals.

Effects of Reverberation and Compression on Consonant Identification in Individuals with Hearing Impairment.

Objectives: Hearing aids are frequently used in reverberant environments; however, relatively little is known about how reverberation affects the processing of signals by modern hearing-aid algorithms. The purpose of this study was to investigate the acoustic and behavioral effects of reverberation and wide-dynamic range compression (WDRC) in hearing aids on consonant identification for individuals with hearing impairment. Design: Twenty-three listeners with mild to moderate sloping sensorineural hearing loss were tested monaurally under varying degrees of reverberation and WDRC conditions. Listeners identified consonants embedded within vowel–consonant–vowel nonsense syllables. Stimuli were processed to simulate a range of realistic reverberation times and WDRC release times using virtual acoustic simulations. In addition, the effects of these processing conditions were acoustically analyzed using a model of envelope distortion to examine the effects on the temporal envelope. Results: Aided consonant identification significantly decreased as reverberation time increased. Consonant identification was also significantly affected by WDRC release time. This relationship was such that individuals tended to perform significantly better with longer release times. There was no significant interaction between reverberation and WDRC. The application of the acoustic model to the processed signal showed a close relationship between trends in the behavioral performance and distortion to the temporal envelope resulting from reverberation and WDRC. The results of the acoustic model demonstrated the same trends found in the behavioral data for both reverberation and WDRC. Conclusions: Reverberation and WDRC release time both affect aided consonant identification for individuals with hearing impairment, and these condition effects are associated with alterations to the temporal envelope. There was no significant interaction between reverberation and WDRC release time.

Intelligibility and clarity of reverberant speech: Effects of wide dynamic range compression release time and working memory

Purpose The purpose of this study was to examine the effects of varying wide dynamic range compression (WDRC) release time on intelligibility and clarity of reverberant speech. The study also considered the role of individual working memory. Method Thirty older listeners with mild to moderately-severe sloping sensorineural hearing loss participated. Individuals were divided into high and low working memory groups on the basis of the results of a reading span test. Participants listened binaurally to sentence stimuli simulated at a range of reverberation conditions and WDRC release times using a high compression ratio. Outcome measures included objective intelligibility and subjective clarity ratings. Results Speech intelligibility and clarity ratings both decreased as a function of reverberation. The low working memory group demonstrated a greater decrease in intelligibility with increasing amounts of reverberation than the high working memory group. Both groups, regardless of working memory, had higher speech intelligibility and clarity ratings with longer WDRC release times. WDRC release time had a larger effect on speech intelligibility under more reverberant conditions. Conclusions Reverberation significantly affects speech intelligibility, particularly for individuals with lower working memory. In addition, longer release times in hearing aids may improve listener speech intelligibility and clarity in reverberant environments.

Listener Factors Associated with Individual Susceptibility to Reverberation

Background: Reverberation is a source of acoustic degradation, present to varying extents in many everyday listening environments. The presence of reverberation decreases speech intelligibility, especially for listeners with hearing impairment. There is substantial variability in how susceptible individuals with hearing impairment are to the effects of reverberation (i.e., how intelligible reverberant speech is to a listener). Relatively little is known about the listener factors which drive that susceptibility. Purpose: To identify listener factors that are associated with an individuals susceptibility to reverberation. Another purpose was to investigate how these listener factors are associated with reverberant susceptibility in relation to the amount of reverberation. The listener factors investigated were degree of hearing loss, age, temporal envelope sensitivity, and working memory capacity. Research Design: This study used a correlational design to investigate the association between different listener factors and speech intelligibility with varying amounts of reverberation. Study Sample: Thirty‐three older adults with sensorineural hearing loss participated in the study. Data Collection and Analysis: Listener temporal envelope sensitivity was measured using a gap detection threshold task. Listener working memory capacity was measured using the Reading Span Test. Intelligibility of reverberant speech was measured using a set of low‐context sentence materials presented at 70 dB SPL without individual frequency shaping. Sentences were presented at a range of realistic reverberation times, including no reverberation (0.0 sec), moderate reverberation (1.0 sec), and severe reverberation (4.0 sec). Stepwise linear regression analyses were conducted to model speech intelligibility using individual degree of hearing loss, age, temporal envelope sensitivity, and working memory capacity. A separate stepwise linear regression model was conducted to model listener speech intelligibility at each of the three levels of reverberation. Results: As the amount of reverberation increased, listener speech intelligibility decreased and variability in scores among individuals increased. Temporal envelope sensitivity was most closely associated with speech intelligibility in the no reverberation condition. Both listener age and degree of hearing loss were significantly associated with speech intelligibility in the moderate reverberation condition. Both listener working memory capacity and age were significantly associated with speech intelligibility in the severe reverberation condition. Conclusions: The results suggest that suprathreshold listener factors can be used to best predict speech intelligibility across a range of reverberant conditions. However, which listener factor(s) to consider when predicting a listeners susceptibility to reverberation depends on the amount of reverberation in an environment. Clinicians may be able to use different listener factors to identify individuals who are more susceptible to reverberation and would be more likely to have difficulty communicating in reverberant environments.

Combined effects of amplitude compression and reverberation on speech modulations

It is well documented that reverberation in listening environments is common, and that reverberation reduces speech intelligibility for hearing impaired listeners. it has been proposed that multichannel wide-dynamic range compression (mWDRC) in hearing aids can overcome this difficulty. However, the combined effect of reverberation and mWDRC on speech intelligibility has not been examined quantitatively. In this study, 16 nonsense syllables (/aCa/ format) recorded in a double-walled sound booth were distorted using virtual acoustic methods to simulate eight reverberant listening environments. Each signal was then run through a hearing-aid simulation which applied four-channel WDRC similar to that which might be applied in a wearable aid. Compression release time was varied between 12 and 1500 ms. Consonant confusion matrices were predicted analytically by comparing the similarity in the modulation spectra for clean speech and compressed reverberant speech. Results of this acoustical analysis suggest that ...

Songlike vocalizations from a Sumatran rhinoceros calf (Dicerorhinussumatrensis)

Within the last ten years the Sumatran rhino population has dropped 50%, and only 200–300 individuals exist, with five in captivity. Their native habitat is dense tropical forest and they are solitary, therefore much of their behavior remains unknown. Sumatrans are the smallest living rhino, standing 0.9–1.5 m tall, and are covered in coarse, reddish‐brown hair. The first Sumatran rhinoceros born in captivity in 112 years, and the first calf ever recorded, is 17 months old and weighs 448 kg. At the Cincinnati Zoo this male calf was recorded from 1–3 m, using two Statham radio microphones, and one TCD‐D8 Sony DAT recorder (9 Hz–22 kHz). Analysis, including power spectrums, spectrographic functions, and cross correlations were performed using National Instrument’s Polynesia. Preliminary analysis indicates that the calf’s vocalizations are similar in structure to adult Sumatran vocalizations, although there are some distinctions. ‘‘Eeps’’ and ‘‘whales’’ that are found in adult repertoires are produced by the...

Effects of varying reverberation on music perception for young normal-hearing and old hearing-impaired listeners

Reverberation enhances music perception and is one of the most important acoustic factors in auditorium design. However, previous research on reverberant music perception has focused on young normal-hearing (YNH) listeners. Old hearing-impaired (OHI) listeners have degraded spatial auditory processing; therefore, they may perceive reverberant music differently. Two experiments were conducted examining the effects of varying reverberation on music perception for YNH and OHI listeners. Experiment 1 examined whether YNH listeners and OHI listeners prefer different amounts of reverberation for classical music listening. Symphonic excerpts were processed at a range of reverberation times using a point-source simulation. Listeners performed a paired-comparisons task in which they heard two excerpts with different reverberation times, and they indicated which they preferred. The YNH group preferred a reverberation time of 2.5 s; however, the OHI group did not demonstrate any significant preference. Experiment 2 examined whether OHI listeners are less sensitive to (e, less able to discriminate) differences in reverberation time than YNH listeners. YNH and OHI participants listened to pairs of music excerpts and indicated whether they perceived the same or different amount of reverberation. Results indicated that the ability of both groups to detect differences in reverberation time improved with increasing reverberation time difference. However, discrimination was poorer for the OHI group than for the YNH group. This suggests that OHI listeners are less sensitive to differences in reverberation when listening to music than YNH listeners, which might explain the lack of group reverberation time preferences of the OHI group.

Effects of reverberation, background talker number, and compression release time on signal-to-noise ratio

Wide dynamic range compression (WDRC) processing in hearing aids alters the signal-to-noise ratio (SNR) of a speech-in-noise signal. This effect depends on the modulations of the speech and noise, input SNR, and WDRC speed. The purpose of the present experiment was to examine the change in output SNR caused by the interaction between modulation characteristics and WDRC speed. Two modulation manipulations were examined: (1) reverberation and (2) variation in background talker number. Results indicated that fast-acting WDRC altered SNR more than slow-acting WDRC; however, reverberation reduced this difference. Additionally, less modulated maskers led to poorer output SNRs than modulated maskers.

The interaction between reverberation and digital noise reduction in hearing aids: Acoustic and behavioral effects

Digital noise reduction (DNR) is widely implemented in hearing aids to improve the signal-to-noise ratio (SNR) of speech-in-noise. To accomplish this, the DNR processor must be able to accurately discriminate the speech versus noise signals. Acoustically, reverberation causes the blending of the speech and noise signals. The purpose of the present experiment was to examine whether reverberation impacts the benefits of DNR processing. Speech stimuli were combined with white noise at multiple SNRs. Speech-in-noise signals were processed using virtual auditory space techniques to simulate reverberation times and with a DNR simulation that mimicked hearing aid processing based on spectral subtraction. Signals were acoustically analyzed to quantify changes in SNR as a result of DNR processing. As reverberant degradation increased, the improvement in SNR decreased. Behaviorally, hearing-impaired individuals listened to low-context sentences in noise with varying reverberation either with or without DNR processi...

The role of modulation characteristics on the interaction between hearing aid compression and signal-to-noise ratio

Hearing aids use compression amplification to provide greater gain to lower amplitude sounds than higher amplitude sounds. When there are two signals (i.e., speech-in-noise) hearing aids alter the signal-to-noise ratio (SNR) by disproportionately increasing the lower amplitude signal compared to the higher amplitude signal. The purpose of the present study was to examine the relationship between hearing aid compression and SNR alteration along a continuum of signal modulation characteristics. Sentence stimuli were combined with either 1-, 2-, or 6-talker modulated noise at a range of SNRs. Speech-in-noise signals were processed at a range of reverberation times with the speech and noise signals co-located. Stimuli were then processed at a range of compression release times (RT) using a hearing aid simulation which mimicked six-channel hearing aid processing. Signals were acoustically analyzed using a digital inversion method which employed phase cancellation to separate speech and noise signals at the out...