Intelligibility Based Automatic Volume Control for Public Address Systems

Intelligibility Based Automatic Volume Control for Public Address Systems

Oosterom, J.A.

Heusdens, R. (mentor)
Hendriks, R.C. (mentor)
Van der Schaar, H.S.P. (mentor)

Electrical Engineering, Mathematics and Computer Science

Mediamatics

Embedded Systems

2011-07-05

To convey messages to the public, public address systems (PA) are installed in buildings and at venues. These messages generally contain important information for the listener. This information has to come across well, i.e. the message should be intelligible. Because the environment, and mainly the background noise, can change over time, it is important for a public address system to adapt accordingly, so that the intelligibility of the messages is maintained. To maintain the intelligibility automatic volume control algorithms are used. In current solutions these algorithms adapt the volume to maintain the signal to noise ratio at a constant level. Such approaches require acquiring information about the noise from a sensing microphone. The difficulty in this is that the sensing microphone not only captures the noise, but also the signal coming from the PA itself, including its echoes and reverberations. To avoid the signal separation problem, the proposed solution directly analyses the intelligibility of the message using the signal from the sensing microphone. For this an objective intelligibility method was used, that analyses correlations between the original clean message and the distorted message, from the microphone. Using the found intelligibility, the volume is controlled to maintain intelligibility. However, because maximum intelligibility occurs at the maximum volume of the PA system, before the signal starts deforming, maintaining intelligibility alone is not enough. Loud PA systems are perceived to be annoying especially if the background noise is low. That is why the proposed solution limits the loudness of the PA system in combination with maintaining the intelligibility.

Volume
Intelligibility
Public Address

http://resolver.tudelft.nl/uuid:5c7870c6-655d-4200-a37e-096c46790100

2011-07-08

Student theses

master thesis

(c) 2011 Oosterom, J.A.