Quite often, meetings come to a screeching halt thanks to a gnarly sound called feedback. Feedback is an annoying and potentially damaging squealing or humming sound that is extremely distracting during meetings. Apart from it being a distraction, it may force the participants to stop the meeting and address the issue thereby affecting productivity.
While feedback loops are a common occurrence and unavoidable when working with audio technology, there are ways and means to limit or control it. In this blog, we explain why feedback occurs, its impact on meetings and tips to avoid and eliminate it.
What is feedback?
Feedback occurs when an audio signal emanating from the loudspeakers is introduced in the in the microphone’s signal chain both in phase and at a suitable level. This signal is picked up and gets looped through the system. The signal is then amplified again and played back through the loudspeakers. One or more frequencies may begin to ring or howl and produce a terrible and unpleasant noise.
Every audio system has a maximum amount of gain or volume that can be applied before feedback is introduced which is known as gain before feedback. Some of the key reasons for feedback in meeting rooms are high gain levels, improper placement of speakers and microphones, number of open mics (NOM), and room acoustics among others.
Tips to reduce feedback in meeting rooms
- Move the microphone closer to the sound source
Poor microphone placement increases the amount of gain required in order to capture sound. The higher the gain, the closer you are to introducing feedback loops. This can be avoided by placing the microphones closer to the sound source or participant.
- Reduce the number of open microphones
Every time the number of open microphones is doubled, the amount of available potential gain is reduced by nearly three dB. Additionally, unwanted noise is introduced into the system which presents additional paths for potential feedback loops to occur. If possible, you can encourage users to mute their microphones when they are not speaking.
- Move the loudspeakers closer to the listener
When the loudspeaker is away from the listener, higher volume is required to achieve optimum coverage area. You can opt for distributed ceiling loudspeakers to ensure even coverage. Additionally, you can use delayed surface mount loudspeakers to provide a suitable level to participants seated further away.
- Use directional microphones
Omnidirectional microphones are designed to capture sound from all directions, on the other hand, microphones with cardioid or super cardioid capsules offer higher directionality in terms signal pickup. Strategically placed directional ceiling or surface-mounted microphones help minimise any unwanted noise from entering your system and maximises the amount of gain available.
- Consider signal processing
Many modern dedicated signal processors offer built-in feedback reduction and Acoustic Echo Cancellation. This process introduces feedback into the system and then applies notches in the equalization to reduce those troublesome frequencies. Although this can also be done manually with a parametric EQ, in meeting room it is based to opt for a DSP with feedback reduction. Not only do they minimize feedback, they also improve the intelligibility of sound.
- Consider acoustic treatment
Each room has certain frequencies that are more resonant than others. Hard and reflective surfaces such as glass window panes or hardwood tables contribute to that reverberant field. You can use absorption material to reduce the amount of reverb and reverberant field. This ensures that more direct sound is reaching the audience, thereby requiring less gain to ensure good intelligibility. Acoustic treatment also helps in controlling unwanted ambient sounds.
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