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Get The Decibel Level From A Mic In Rust

This is what I'm using for ASCII _ BEAR to move the mouth when I speak into the mic with enough volume :

#!/usr/bin/env cargo +nightly -Zscript

//! ```cargo
//! [dependencies]
//! anyhow = "1.0.75"
//! clap = "4.4.7"
//! cpal = "0.15.2"
//! ```

use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};

fn main() -> Result<(), anyhow::Error> {
    let host = cpal::default_host();
    let device = host.default_input_device().unwrap();
    let config: cpal::StreamConfig = device.default_input_config().unwrap().into();
    let input_sender = move |data: &[f32], _cb: &cpal::InputCallbackInfo| {
        let x: f32 = data[0];
        if x > 0.006 {
            println!("{}", x);
    let input_stream = device
        .build_input_stream(&config, input_sender, err_fn, None)
    let _ = input_stream.play();

fn err_fn(err: cpal::StreamError) {
    eprintln!("an error occurred on stream: {}", err);

- This outputs the dB level to the terminal

- The samples happen non - stop. I put a check in place so the values only output if they are greater than 0.006

- I've seen negative numbers coming from the float values as well. I'm not sure what's happening with those (I've only got a single channel in my setup so I don't think it's a stereo thing)

- There's a very slight delay on my setup from the time I speak until the output shows up. I got through a DAC which might have something to do with it, or that might just be how it works. I'm not super worried about it for now

Footnotes And References