Good Quality Audio Sensor

Using Arduino Audio
1

I need an audio sensor (for an electret mic) that is high quality AND one where I can add my own potentiometer to adjust for the sensitivity. I know I want an analog sensor.

I know I need a steady 2 to 2.5v signal with ac signal between - top (no higher than 5v positive) and bottom (no lower than 0v positive).

I realize that most of the electret mics for arduino work like this anyway, but I get varying qualities and I don't really like the on-board potentiometers. I suppose the on-board is to adjust for the voltage you decide to use (between 3v and 12v).

I'm pretty sure I want to run at 3v from my nano. Any suggestions? Should I just make my own circuit and the heck with the pre-made sensor?

2

[u]Here is the schematic[/u] for the SparkFun microphone board. If you want to build your own, that's a good place to start.

It's got all of the "elements" - Power for the electret mic, amplification, and output biased at half the power supply.

You can adjust the gain by changing the values of R4 or R5, or you can use a pot as R5. Or, you can stick a volume-control pot between C1 & R4, etc.

Choose a "rail to rail" op-amp to maximize voltage swing relative to power supply voltage.

What do you mean by "high quality"?

I know I need a steady 2 to 2.5v signal with ac signal between...

Of course, you'll need a steady tone at a constant distance (with little acoustical noise) in order to get a steady electrical signal. :wink:

3

High quality I meant a circuit that doesn't pick up a lot of noise. Don't want noise being mistaken for audio signal. I will check out that sparkfun you sent me. Thank you!

4

High quality I meant a circuit that doesn't pick up a lot of noise. Don't want noise being mistaken for audio signal.

Any mic will pick-up acoustical noise like any other sound. Acoustic noise is usually the biggest issue. A directional mic* can sometimes help because it reduces sound from other directions, where a standard (omnidirectional) mic picks-up sound (including noise) from all around.

Besides having a quiet environment, a stronger signal will give you a higher signal-to-noise ratio. That means a loud source close to the microphone. i.e. If you record someone speaking from across the room, you'll get a lot of noise in the recording. And, you are more likely to notice the noise in the recording than to notice it "live".

Electrical noise can be minimized by using a well-filtered power supply, a metal shielding box, a low noise preamp, and low input impedance (which you already have with an electret mic). Power supply noise (AC hum or switching noise from a switching power supply) is the most common source of electrical noise with a low impedance preamp. With a high-impedance input (such as a guitar input) shielding becomes very important.

If you are making a high-quality preamp, you have to minimize ALL sources of electrical noise. And if you want a high quality recording, you need a good microphone and a good "signal" in a soundproof studio with good acoustics. (Although you are probably not recording, the principals for a high quality signal are the same.)

  • Microphones are made directional by their mechanical design. So, you can't buy a directional electret element, but you can buy a directional (cardioid) stage/studio mic,
5

All very good information - thank you! As far as a quality preamp, what is a good choice? Is there an ic chip that would work better than others? Tried the 386D and not thrilled with it.

I will stick with the electret mic because I won't be sure which way the sound may come from.