Instrumentation for Basic Research in Communication and Hearing Protection Systems
Abstract
This DURIP grant supported instrumentation to perform basic research in control theory, hearing protector design, and psychoacoustics. The research is aimed at developing and evaluating hearing protection and communication systems for environments in which the user is exposed to high levels of nonstationary noise. The instrumentation provided by this grant consists of an Artificial Head Measurement System, a Low Frequency Acoustic Test Cell, a vibration isolation table, and digital signal processing equipment for rapid prototyping of active noise reduction (ANR) algorithms based on feedforward adaptive filters. During the performance period, the instrumentation directly supported graduate and undergraduate research work on hybrid ANR system and speech intelligibility metrics. Tests of hybrid ANR systems, using both feed-forward and feed-back control, were conducted using aircraft noise. The report covers the instrumentation and its costs along with the research work that it supported. Research projects included the development of a digital, hybrid ANR system using feedforward adaptive control for hearing protection. The system consists of a Lyapunov-tuned LMS filter and a digital feedback ANR system. Another project focused on the effects of speaker dynamics on ANR. This work characterized a variety of off-the-shelf speakers and evaluated the use of a filtered-X LMS filter for flattening the transfer function from the speaker to error microphone, versus using digital equalization to flatten the response. In another project, testing provided evidence that ANR improves speech intelligibility through reduction of low frequency noise. The final project dealt with the development of hearing protection for extreme noise fields. In addition to passive and active noise reduction of the air transmission path, active structural control and passive noise control through design of the helmet structure may be required to reduce bone conducted noise through the skull. (9 refs7
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 16, 2004
- Accession Number
- ADA424702
Entities
People
- Laura Ray