36 CFR Parts 1190 and 1191 ADA and ABA Accessibility Guidelines - Preamble (Discussion of Comments and Changes)

Section 706.3 specifies that receivers required to be compatible with hearing aids (25%) must be neck loops since this type interfaces with hearing aid T-coils. Many comments supported this provision and no changes to it have been made in the final rule.

The performance of assistive listening systems is a concern among users. The quality and capability of systems largely determine the quality of sound transmission. Sound quality, internal noise, signal-to-noise ratio, signal strength, and boost vary among products. As a result, some systems do not adequately meet the needs of people who are hard of hearing. For example, the boost of some products may amplify sound adequately for people with mild hearing loss but not for those with profound hearing loss.

In the belief that standards should be developed to provide guidance in selecting products of sufficient quality and capability, the Board funded a study on assistive listening systems that was completed in 1999. Conducted by the Lexington Center, this project included collecting information on assistive listening systems, a review of the state-of-the-art with respect to assistive listening systems, and a survey of consumers, service providers, dispensers and manufacturers to determine how effective assistive listening systems are at present and what the major problems, limitations, and complaints are regarding existing systems. With this information, the researchers developed objective means for specifying the overall characteristics of any assistive listening system, from sound source to listener’sear, to be able to predict how well the system will work in practice and to determine objective criteria for establishing guidelines or recommendations for the use of assistive listening systems in public places.

The criteria recommended by this research include:

• a signal-to-noise ratio of at least 18 decibels measured at the earphones

• the capability of receivers to deliver a signal with a sound pressure level of at least 110 decibels and no more than 118 decibels with a dynamic range on the volume control of 50 decibels

• peak clipping levels at or below 18 decibels down from the peak level of the signal

Comment. The Board sought comment on whether the criteria developed through the Lexington Center research should be included in the final rule (Question 30). Commenters overwhelmingly supported the inclusion of specifications for the performance and sound quality of assistive listening systems.

Response. The Board has included performance criteria for assistive listening systems based on the Lexington Center research that address the sound pressure level (706.4), signal-to-noise ratio (706.5), and peak clipping level (706.6).

A report from the Lexington Center on this research, "Large Area Assistive Listening Systems: Review and Recommendations," is available from the Board and its website at www.access-board.gov. Additional resources stemming from the project, including a series of technical bulletins on assistive listening systems, are also available.