Polycom SoundStructure C16 Design Manual page 213

Hide thumbs Also See for SoundStructure C16:

Table of Contents

To properly adjust the levels for microphones, adjust the analog input gains so that during normal speech

at the desired distance from the microphones two yellow LEDs are reached by the peak meter and

occasionally additional LEDs are flickering above that. The VU meter should show a solid green LED at the

The following figure shows examples of peak signal levels that are too low, just right, and too high during

normal conversational speech at the desired distance from the microphone.

Peak Signal Gains

If the meter levels are too low for a given microphone and for the desired distance from the microphone,

increase the input gain slider to add more gain to the signal in the analog domain. As a starting point for

adjusting gains, consider the following table that lists microphone sensitivities with the analog input gain

required to create a 0 dBu nominal signal level in the SoundStructure products assuming a 72dB SPL audio

signal at the microphone. The sensitivity information includes both dBV/Pa and mV/Pa formats and the

microphone gains in this table have been rounded to the nearest 0.5dB.

SoundStructure devices provide up to 64dB of analog gain to support microphones with sensitivities as low

as -44 dBV/Pa (or 6.3 mV/Pa). Microphones that have a lower sensitivity may require additional external

signal gain to provide enough gain to get to the 0 dBu nominal signal level. A microphone with higher

sensitivity means that less gain is required to achieve a 0dBu nominal signal when a 72dB SPL signal is

present at the microphone.

For example, a common tabletop microphone has a sensitivity of -27.5 dBV/Pa. which translates to an input

gain of 48dB.

Sensitivity Information for Tabletop Microphones

Sensitivity (dBV/Pa)

Polycom, Inc.

Microphone gain (dB)

Sensitivity (mV/Pa)

Troubleshooting