What is the Larsen effect?

Annoying-noise-001

We are proud to open our sound area by introducing one of the most common problems that can occur at any sound installation. It is known as Larsen effect, also known as feedback effect. This effect is produced when a sound signal that has already been amplified and reproduced by a loudspeaker is again captured by a microphone. This cause of events creates a specific annoying sound that can be familiar to most of the people. The real problem is that due to this effect we are forced to reduce the volume level of the system and as a result its performance is decreased. In this article we will analyze the causes of this effect as well as different ways to solve it.

●  CAUSES

audio-feedback

As we previously were explaining, the Larsen effect is produced when a sound signal coming from a loudspeaker is again captured, re-amplified and sent again to the loudspeaker. This feedback process happens so quickly that automatically causes a tone of a specific frequency which in sound terms is translated to the annoying sound we mentioned before. This frequency, or tone, can vary depending on the distance between the speaker and microphone. 

 

●  SOLUTIONS

There is a variety of solutions to this problem that could be ordered by its complexity in performance. We recommend the following solutions:

-          Be sure that the microphones are located behind the speakers. This way the direct audio signal coming from the speaker will be captured by the microphone with an important attenuation, no matter the size of the room. Thus we will avoid the signal to be re-amplified.

-          Use microphones with a high directivity according to its specifications and also try to use them as close as possible to the speaker’s mouth.

-          By adding an equalizer to the sound system you will have the tool to locate the annoying frequency and then reduce it as much as possible.

Considering that this problem appears within a high frequency, at UDE we work every day to improve our service and therefore we focused on an alternative that could be more efficient as well as transparent. This is the reason why we introduced in the market a feedback suppressor module (WXD-19) that can be inserted inside any UDE amplifier or preamplifier. This module function consists of essentially causing a dynamic phase shift to the audio signal. This way the feedback effect is completely removed. This alternative has successfully been used in areas where the solutions posted above were not enough to guarantee the solution to this problem.