Need Recommendations for Microphone Module for dB SPL Monitoring

Other Hardware General Electronics
1

Hello forum,

I'm looking for a microphone module to monitor dB SPL levels, but I've encountered issues with MAX9814's automatic gain control falsifying readings. Here are my criteria for a new module:

  • Atleast 66 dB SPL maximum range
  • Small: No larger than a matchbox
  • No automatic gain control
  • Low recovery time: I'll be performing averaging calculations

Modules I wanted to use but couldn't:

  • Adafruit SPW2430: Won't return to base voltage immediately (Post)
  • Sparkfun BOB-12578: Pricy shipping

If you have any recommendations or alternative options that meet the criteria, I would greatly appreciate your help. Thanks

2

My application requires a set of readings as far back as the previous hour, specifically for monitoring the following continuously:

  • Hourly average: ≤ 50 dB SPL
  • 90th percentile: ≤ 55 dB SPL
  • Maximum: ≤ 66 dB SPL
3

I would recommend this product:
Gravity: Analogue Sound Level Meter.

Sound Level Meter

It has an output that is already calibrated, and is 50dBA/volt.
Just measure the output voltage in volts and multiply by 50 and you have the sound pressure level.

There is a Wiki for it here.

It might not fit in your matchbox though.

3 Likes
4

The AGC on the MAX9814 chip can be disabled (pin 14). That may, or may-not be easily accessible on your particular board.

Quiet sounds can be difficult because of electrical noise in the preamp. I made an SPL meter with the BOB-12758. There are lots of notes, which may be useful... or discouraging...

Weird... You should be able to take-out the slowly-changing bias with a capacitor (a high-pass filter) and then you can use your own bias circuit.

This circuit should work -
Audio Input Schematic

2 Likes
5

Thanks

This should work for my application, but it seems to have the same accessibility issues as the BOB-12758 module

I'll keep it in mind for now

6

Thanks

I've already browsed your project beforehand and it was my reason for considering the BOB-12758 module. Life would be less hard if it weren't as inaccessible to me and I could just plug and play your code with it

For the SPW2340, I'll get myself one and see how it works with your circuit. I'm using an ESP32, so I just have to change the voltage divider for a 3.3V supply. Is that right?

7

Right.

1 Like
8

Here are some relevant options based on your criteria for monitoring dB SPL levels, avoiding AGC, having fast recovery times, and being within a small size:

Knowles MM20-33639-000

  • Type: Analog MEMS
  • Frequency Range: 100 Hz ~ 10 kHz
  • Voltage: 0.9V ~ 1.3V
  • Sensitivity: -56 dB ±3 dB @ 94 dB SPL
  • Size: MEMS microphones are typically small, so this would likely meet your size requirement.
  • Why It Fits: This is an analog MEMS microphone without AGC. It provides a wide enough frequency response for SPL monitoring, and the sensitivity is ideal for dB level detection.

TDK-Lambda ICS-40214

  • Type: Analog MEMS
  • Frequency Range: 10 Hz ~ 10 kHz
  • Voltage: 1.65V ~ 3.63V
  • Sensitivity: -38 dB ±1 dB @ 94 dB SPL
  • Why It Fits: This microphone offers a broader frequency response and greater sensitivity at a higher voltage range, which could make it a more robust option depending on your setup.
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