Anna K. Nabelek

Reverberation as a parameter in clinical testing.

Word identification was measured binaurally and monaurally using the Modified Rhyme Test under noise and reverberation. Normally hearing and hearing-impaired subjects were tested. A change in reverberation time from 0.25 to 0.50 s in a small audiometric room caused a significant change in word identification scores in both groups of subjects. A simulated reverberation composed of five distinct reflections did not affect word identification. The binaural advantage (difference between the binaural and monaural scores) was significant for normally hearing subjects, while it was not significant for hearing-impaired subjects.

Relationship between acceptance of background noise and hearing aid use

Background noise produces complaints among hearing‐aid users, however speech‐perception‐in‐noise does not predict hearing‐aid use. It is possible that hearing‐aid users are complaining about the presence of background noise and not about speech perception. To test this possibility, acceptance of background noise is being investigated as a predictor of hearing‐aid use. Acceptance of background noise is determined by having subjects select their most comfortable listening level (MCL) for a story. Next, speech‐babble is added and the subjects select the maximum background noise level (BNL) which is acceptable while listening to and following the story. The difference between the MCL and the BNL is the acceptable noise level (ANL), all in dB. ANLs are being compared with hearing‐aid use, subjective impressions of benefit (APHAB), speech perception in background noise (SPIN) scores, and audiometric data. Individuals who accept higher levels of background noise are more successful users than individuals who acc...

Relation between measures of speech‐in‐noise performance and measures of efferent activity

Individual differences in auditory perceptual abilities in noise are well documented but the factors causing such variability are unclear. The purpose of this study was to determine if individual differences in responses measured from the auditory efferent system were correlated to individual variations in speech‐in‐noise performance. The relation between behavioral performance on three speech‐in‐noise tasks and two objective measures of the efferent auditory system were examined in thirty normal‐hearing, young adults. Two of the speech‐in‐noise tasks measured an acceptable noise level, the maximum level of speech‐babble noise that a subject is willing to accept while listening to a story. For these, the acceptable noise level was evaluated using both an ipsilateral (story and noise in same ear) and a contralateral (story and noise in opposite ears) paradigm. The third speech‐in‐noise task evaluated speech recognition using monosyllabic words presented in competing speech babble. Auditory efferent activit...

Image method for simulating reverberant room response with directional receiver and source.

Image methods are commonly used for computing and analyzing acoustic responses of enclosures. The image method employed by Allen and Berkley [J. Acoust. Soc. Am. 65, 943–950 (1979)] digitally simulated acoustic echoes in a reverberant room by constructing a discrete‐time impulse response in which each echo contributed a single impulse. The authors assumed a rectangular enclosure with an omnidirectional receiver and an isotropic acoustic source. Their calculation procedure was modified to allow its use with directional receiver and source. Introduction of a nonomnidirectional receiver to the method was accomplished by changing the contribution of each image according to a directional characteristic of a receiver. Introduction of an anisotropic sound source to this method was achieved by assignment of a spatially oriented source characteristic to each source image. The latter approach, however, may no longer be valid because the image method assumes full source symmetry. The usefulness of the proposed modification for small reverberant enclosures was proven by comparing the results of the modified image method with data obtained by a ray tracing technique. [Research supported by the National Institute on Deafness and Other Communication Disorders.]

Physiologic correlates to background noise acceptance

Acceptance of background noise can be evaluated by having listeners indicate the highest background noise level (BNL) they are willing to accept while following the words of a story presented at their most comfortable listening level (MCL). The difference between the selected MCL and BNL is termed the acceptable noise level (ANL). One of the consistent findings in previous studies of ANL is large intersubject variability in acceptance of background noise. This variability is not related to age, gender, hearing sensitivity, personality, type of background noise, or speech perception in noise performance. The purpose of the current experiment was to determine if individual differences in physiological activity measured from the peripheral and central auditory systems of young female adults with normal hearing can account for the variability observed in ANL. Correlations between ANL and various physiological responses, including spontaneous, click‐evoked, and distortion‐product otoacoustic emissions, auditor...

Acceptance of background noise as a function of speech presentation level

The acceptance of background noise while listening to speech (ANL) at different speech presentation levels was assessed. Twenty listeners (10 male) between 18–30 years with normal hearing listened to a narrative at speech presentation levels of 20, 34, 48, 62, and 76 dB HL, then adjusted the background noise to the highest intensity level that they would be willing to accept for an extended listening period. The ANL is the intensity of the speech presentation level minus the intensity level of the background noise. The group mean ANLs for presentation levels of 20, 34, 48, 62, and 76 dB HL were 10.60, 14.25, 17.10, 21.80, and 24.55 dB, respectively. The group mean ANLs differ by approximately three and one half decibels between each presentation level. This difference between adjacent speech presentation levels is representative of a linear function. The average MCL was 43 dB HL with a standard deviation of 6.7 dB. The group mean ANL for speech presented at MCL was 15.5 dB with a standard deviation of 7.2...

Perception of linear formant trajectories in vowels

Boundary locations for identification functions were tested for /i‐eh/ and /u‐i/ continua. In the /i‐eh/ continuum, F1 varied in 14 steps from 360 to 580 Hz, and in the /u‐i/ continuum, F2 varied in 19 steps from 1000 to 2000 Hz. There were five different types of stimuli in each continuum with (1) steady‐state formants, (2) one formant changing linearly over time, and (3) two formants changing linearly. The single changing formant was F1 in the /i–eh/ continuum and F2 in the /u–i/ continuum. The two changing formants were F1 and F2 in both continua. The trajectories had upward or downward directions. Identification functions were obtained with ten normal‐hearing subjects. Directions of boundary shifts for the /i–eh/ continuum indicated a perceptual emphasis of the initial segments of F1 and F2 trajectories. The directions of boundary shifts for the /u–i/ continuum indicated a perceptual emphasis of the final segment of F2 trajectory when only F2 changed over time. However, when changes over time in F1 were added, boundaries for these stimuli were not significantly different from the boundary for the stimuli with steady‐state formants. Differences in perception of F1 and F2 trajectories in two tested continua will be discussed. [Work supported by NIH.]

Comparison of acceptance of background noise and speech reception threshold in quantifying the hearing aid directivity benefit

Hearing aid directivity benefit was compared as improvement in acceptance of background noise and speech reception threshold (SRT). Forty adult subjects were tested wearing binaural hearing aids in omnidirectional and directional listening conditions. Acceptance of background noise was determined by having subjects select their most comfortable listening level (MCL) for a story delivered from a loudspeaker (0). Next, speech babble was added (180) and the subjects selected the maximum background noise level (BNL) which was acceptable while listening to and following the story. The MCL minus the BNL yielded the acceptable noise level (ANL), all in dB. The difference between the ANL for the omni‐directional and directional conditions is the directivity benefit. The SRT was determined by delivering spondaic words (0) at the subjects MCL. Next, speech babble was delivered (180) and adjusted until the subject could repeat 50% of the spondees. The difference between the SRT for the omni‐directional and direction...

Room acoustics needs of people with hearing impairment

Speech perception of people with hearing impairment is negatively affected to a greater degree by background noise and reverberation than the speech perception of people with normal hearing. As a consequence, rooms which have adequate acoustics for normal‐hearing people might be too noisy or too reverberant for hearing‐impaired users. Causes of perceptual difficulties of hearing‐impaired listeners and data comparing effects of noise and reverberation on speech perception of normal‐hearing and hearing‐impaired listeners will be presented. The number of people with hearing loss grows with age. Two major causes are noise exposure and aging processes. People with hearing loss can obtain improvement in speech communication with hearing aids but poor room acoustics can limit hearing benefits and cause hearing aid rejection. Advantages of acoustical modifications, preferential sitting, and use of amplification in small rooms will be discussed. Listening systems such as induction loops, FM, and infrared will be considered as alternatives or additions to acoustical modifications of large rooms. The listening systems can be utilized by hearing aid users and by people who do not use hearing aids, even those with normal hearing.

A linear model of boundary shifts in /v–i/ and /open oh–eh/ continua

Boundary locations were tested for /v–i/ and /open oh–eh/ continua with steady‐state or linearly changing formants in which F2 was varied. F1 and F2 trajectories had upward and downward directions. Boundary shifts were calculated for changing formant stimuli relative to the boundary for steady‐state stimuli. The directions of boundary shifts indicated perceptual emphasis of the final segments of F2 trajectory which might be a consequence of low‐frequency spread of masking from F1 to F2. A linear model was developed in which boundary shifts were related to spectral distance between F1 and F2 trajectories. Parameters were initial and final frequencies of F1 and boundary F2 established for each continuum with steady‐state stimuli. When the distance was constant in time shifts depended on directions of F1 and F2 trajectories, described by two model terms containing differences of initial and final frequencies of F1 and F2. When the distance was changing in time additional shift was toward the greater spectral...