Measurement of attack-Release Times in Compression Hearing Aids

1978 ◽  
Vol 21 (2) ◽  
pp. 338-349
Author(s):  
Jerry L. Punch ◽  
William F. Lawrence ◽  
G. Donald Causey
Keyword(s):  
Hearing Aids ◽  
Phased Array ◽  
Automatic Gain Control ◽  
Gain Control ◽  
Signal Generation ◽  
Graphic Mode ◽  
Release Times ◽  
Basic Protocol ◽  
Mode A

A system for measurement of attack-release times in hearing aids with automatic-gain-control circuitry is described, with a view toward implementing that portion of the ANSI S3.22-1976 Standard in which parameters for these measurements are specified. Signal generation is accomplished by using a phased-array loudspeaker arrangement designed to produce transient-free pulsed acoustic sinusoids. Output waveforms are captured by a commercial transient recorder, and are displayed in either an oscilloscopic or graphic mode. A specific means of calculating attack and release times is recommended whereby variously shaped output waveforms are amenable to the basic protocol outlined in the ANSI Standard.

Performance of New Hearing Aids Using the ANSI S3.22–1976 Standard

1982 ◽  
Vol 47 (4) ◽  
pp. 376-382 ◽  
Author(s):  
Thomas H. Townsend ◽  
Clifford C. Olsen
Keyword(s):  
Hearing Aids ◽  
Automatic Gain Control ◽  
Gain Control ◽  
Test Apparatus

One hundred new hearing aids were tested to determine their compliance with ANSI S3.22–1976 specifications. Thirty-four models representing eight manufacturers were included. Estimates of the test equipment's accuracy were utilized as required by the standard to correct the tolerances permitted for the 11 measurements made. Results revealed that 68% of the instruments tested met all specifications, when the accuracy of the test apparatus was accounted for, while 11% fewer hearing aids passed all tests when it was excluded. No greater than a 10% difference was found in the performance of various types of aids, such as automatic gain control, directional, linear, or nondirectional.

Optimization of a slow-acting automatic gain control system for use in hearing aids

1991 ◽  
Vol 25 (3) ◽  
pp. 171-182 ◽  
Author(s):  
Brian C. J. Moore ◽  
Brian R. Glasberg ◽  
Michael A. Stone
Keyword(s):  
Control System ◽  
Hearing Aids ◽  
Automatic Gain Control ◽  
Gain Control

Input Stimuli for Obtaining Frequency Responses of Automatic Gain Control Hearing Aids

1989 ◽  
Vol 32 (1) ◽  
pp. 189-194 ◽  
Author(s):  
David A. Preves ◽  
Lucille B. Beck ◽  
Edwin D. Burnett ◽  
Harry Teder
Keyword(s):  
Frequency Response ◽  
Hearing Aids ◽  
Input Signal ◽  
Pure Tone ◽  
Automatic Gain Control ◽  
Broad Band ◽  
Gain Control ◽  
Response Curves ◽  
Frequency Responses ◽  
Band Noise

Developing a family of frequency response curves for AGC types of hearing instruments using swept pure tones at varying input levels often produces erroneous results. This problem is caused by exceeding the threshold for activating the AGC circuit at some frequencies but not at other frequencies during the pure-tone sweep, thereby producing a different frequency response from that which would be obtained with a complex input signal such as speech-shaped noise. This measurement artifact may be minimized by ensuring that the threshold for activating the AGC circuit is either always exceeded or never exceeded during the development of a frequency response curve. Three input signals are compared for developing a family of frequency responses for an AGC hearing aid: (1) swept pure tone, (2) swept pure tone with bias tone added, and (3) shaped broad-band noise. The shaped broad-band noise appears to be the input signal of choice.

Compression Amplification in Hearing Aids

1994 ◽  
Vol 3 (3) ◽  
pp. 51-65 ◽  
Author(s):  
Louise M. H. Hickson
Keyword(s):  
Hearing Loss ◽  
Hearing Aids ◽  
Single Channel ◽  
Automatic Gain Control ◽  
Gain Control ◽  
Volume Control ◽  
Profound Hearing Loss ◽  
Systems Research ◽  
Research Findings ◽  
Adaptive Recovery

In this tutorial, the characteristics of compression amplification in analog hearing aids and the experimental results obtained with single- and multichannel compression amplification systems are reviewed. Single-channel compression systems are classified into four broad groups on the basis of their static and dynamic characteristics: compression limiters, syllabic compressors, automatic volume control (AVC) systems, and "others," those with adaptive recovery time (aRT) and dual frontend automatic gain control (AGC) (Moore, 1990; Moore & Glasberg, 1988). Multichannel compression devices have, to date, used a variety of different types of compression, with syllabic compression in each frequency channel being the most popular. Experimental evidence suggests that compression limiting is generally superior to peak clipping as a means of controlling output, except for some individuals with severe to profound hearing loss. There is some evidence that syllabic compression and AVC systems enhance speech perception in quiet compared to conventional linear amplification; however, this improvement is not consistently maintained in the presence of background noise. The majority of recent research has focused on multichannel compression, and favorable results have been obtained with some systems. Research findings about the efficacy of using compression amplification for people with hearing loss have been extremely variable, and possible reasons for this are discussed.

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