Controlling Sound Level- Mechanical Method

There are two ways to control sound level in an electronic audible alarm. One is mechanical and the other is electrical. The mechanical method involves changing the size of the front hole opening of the audible alarm. The open area in the front of the audible alarm including the front hole opening is an acoustically tuned cavity. By partially covering the front hole opening, you are changing the cavity tuning making it less efficient. The more the front hole opening is covered, the more the sound level will decrease.

An example of how to do this is shown above. The picture above shows our manual sound baffle accessory with part number: SCVC being assembled onto the front of a panel mount alarm housing. The SCVC accessory consists of a screw and two pieces of plastic. After the sound baffle is attached to the front of the alarm, the sound level can be changed by manually turning the top piece of plastic. The sound level of the alarm will attenuate anywhere from 10 to 15 dB’s making the alarm sound about half as loud as before.

The main disadvantage of this manual method of controlling the sound level is that it is controlled by the operator. In some situations, it is dangerous to let the operator have the ability to decrease the sound level of the alarm. The most obvious potential problem is that the operator could turn the sound level down too much so that the alarm will not easily be heard the next time it is activated. In cases like this, you might want to consider controlling the sound of the alarm electronically (see Technical Bulletin # 06-05).