Squelch and Gain

Introduction

In order to accommodate a wide range of audio inputs and string lengths, we have added user configurable squelch (noise reduction) and gain controls on the LED settings page for the volume reactive animations.

Squelch

Adjust this value on the LED Settings page so that the leds are only activated above a certain 'background noise' level.

Gain

Line-in signals are typically much lower than that of some of the microphones. Rather than use an auto gain function, you can manually adjust the gain from 0 to 255, which translate to a 1.0 gain up to a 5.0 gain.

Manual Calibration

The sound reactive fork of WLED supports several different types of inputs. In addition, different environments can have different levels of ambient/background noise. As a result, we've included settings for adjust gain and reduce sensitivity to background noise.

1. Start out with the routine '*Gravcenter' with default sliders in the middle.
2. Go to the sound settings configuration page.
3. Increase gain to a high value, let's say 25 (or higher) and set the squelch to '0' and save.
4. You should now see the led's flashing.
5. Increase and save the squelch in a quiet setting until the lights are no longer flashing.
6. Once that's done, make noise appropriate to your 'noisy' environment and number of leds. Then adjust/save the gain so that the led's are responding appropriately.
7. Note that some of the animations allow further sensitivity adjustment with the 'Intensity' setting.
8. Check out the 'Sound Reactive Animations' page to see what controls are available for each animation.

Voltage Fluctuation

From faulty microphones to flaky wiring, the ESP8266, getting reliable and spike free sound sampling with WLED and in particular analog microphones has been a challenge. This can be as a result of using the WiFi, especially in AP mode, with the noise it creates, and its draw on the power supply. Digital microphones such as the INMP441, the ICS-43434 or a line-in provide the best results.

Tables of Approximate Values

For your microphone/line-in signal, adjust the squelch to reduce background noise and the gain settings in order to maximize the led activity.

Calculation: sample = sample*sampleGain/40+sample/16;

0 = .0875 gain, 38 = 1.0 gain, 78 = 2.0 gain, 118 = 3.0 gain, 158 = 4.0 gain, 198 = 5.0 gain, 238 = 6.0 gain.

The first table uses FG085 Sinewave generator providing P-P output @ 100Hz. This is used to understand the voltages produced by various inputs. This table was used to configure an animation that reacted the same at different input levels.

Note: Since creating these tables, I've fine tuned the gain formula. Just like Pirates of the Caribbean, consider this as more of a guideline.

Generator setting	Squelch	Gain	Comments
Line-In (FG085) 100Hz@ 4.0V	Sq: 5	Gain: 0	I don't want to go higher.
Line-In (FG085) 100Hz@ 2.4V	Sq: 5	Gain: 64	=2.0X multiplier
Line-In (FG085) 100Hz@ 1.5V	Sq: 5	Gain: 128	=3.0X multiplier
Line-In (FG085) 100Hz@ 1.1V	Sq: 5	Gain: 192	=4.0X multiplier
Line-In (FG085) 100Hz@ 0.9V	Sq: 5	Gain: 255	=5.0X multiplier

Using a pink noise generator from https://www.youtube.com/watch?v=WJ9Go1PnAVA

Device	Squelch	Gain	Comments
Line-In (Hyper-X Gaming Headset)	Sq: 5	Gain: 255	Goes to about 70% if everything is turned up to full. Uses 3.5mm output of USB based Hyper X gaming headset.
Line-In Laptop	Sq: 5	Gain: 140	The laptop produced a significantly higher voltage than the headset.
Line-In (Android)	Sq: 5	Gain: 160	About the same as a standard line-in.

Providing ~80 dB of Pink noise to speaker from https://www.youtube.com/watch?v=WJ9Go1PnAVA As measured by an Android based sound analyzer app.

Microphone	Squelch	Gain	Comments
MAX9814 @60 dB	Sq: 25	Gain: 11	A noisy microphone configuration. Not recommended due to squelch setting.
MAX9814 @50 dB	Sq: 12	Gain: 63	A reasonable configuration.
MAX9814 @40 dB	Sq: 10	Gain: 112	A good configuration.
INMP401	Sq: 6	Gain: 64	I'd like to like this microphone, but have had a lot of bad ones (from China).
MAX4466 (midway)	Sq: 6	Gain: 82	This is a nice microphone that needs a bit of a boost.
MAX4466 (full CCW)	Sq: 6	Gain: 65	Seems OK.
MAX4466 (full CW)	Sq: 8	Gain: 110	Seems OK.
INMP441 (not yet integrated)	Sq:	Gain: 0	Wow! This thing is an amplification beast!