Ever been driving down a quiet suburban street pleasantly listening to your car stereo and then turn onto a busy, noisy road and find that you need to turn up the volume? Or have you ever been at a party where the music is being played at a comfortable level and notice the music becomes increasingly difficult to hear as more people arrive? If the answer’s yes to either of these questions, then you are aware of the annoying problem our ‘loudness control’ device aims to overcome.

In modern stereo systems the volume of the sound produced is controlled at the absolute level using a volume control. However, the sound heard is often affected by the change in noise in the vicinity of the listener. The purpose of our “loudness control device” is to detect these changes in noise and automatically adjust the sound produced depending on the type of noise detected, maintaining a constant volume to the listener without anyone having to touch a dial.

Sounds are made up of a complicated mixture of different frequencies. However, usually sounds are concentrated about certain frequencies more than others. For example, most of the energy generated from people chattering would be concentrated about 3.5kHz. Therefore, instead of raising the entire volume level of the stereo to overcome this noisy chatter, an increase in gain at around 3.5kHz of the music will compensate for this noise. This project utilizes this principle.

The loudness control device uses a microphone to capture the sound (music from the stereo plus the noise in the vicinity) in the room/car and converts it to an electrical signal. This electrical signal is compared to the output of the stereo (electrical signal output before the speakers that is, free of noise) over several frequency bands. If there is a difference in level in any of these of bands, then the music is automatically equalized to compensate for this difference.

Although there are products on the market which achieve similar purposes, they are usually very expensive. Our team aims to design an affordable and effective product which will solve this annoying problem experienced by every person who owns a stereo.

Dr Sarah Dods, Stephen Inglese, David Cox, Meg Batchelor