cpx_sound_meter.py

import array
import audiobusio
import board
import math
import neopixel

CURVE = 2
SCALE_EXPONENT = math.pow(10, CURVE * -0.1)

PEAK_COLOR = (80, 0, 255)
NUM_PIXELS = 10
NUM_SAMPLES = 160


def constrain(value, floor, ceiling):
    return max(floor, min(value, ceiling))


def log_scale(input_value, input_min, input_max, output_min, output_max):
    normalized_input_value = (input_value - input_min) / (input_max - input_min)
    return output_min + math.pow(normalized_input_value, SCALE_EXPONENT) * (output_max - output_min)


def normalized_rms(values):
    minbuf = int(mean(values))
    return math.sqrt(sum(float(sample - minbuf) * (sample - minbuf) for sample in values) / len(values))


def mean(values):
    return sum(values) / len(values)


def volume_color(i):
    return i * (255 // NUM_PIXELS), 50, 0


pixels = neopixel.NeoPixel(board.NEOPIXEL, NUM_PIXELS, brightness=0.1, auto_write=False)
pixels.fill(0)
pixels.show()

mic = audiobusio.PDMIn(board.MICROPHONE_CLOCK, board.MICROPHONE_DATA, frequency=16000, bit_depth=16)
samples = array.array('H', [0] * NUM_SAMPLES)
mic.record(samples, len(samples))
input_floor = normalized_rms(samples) + 10

# Lower number means more sensitive - more LEDs will light up with less sound.
sensitivity = 500
input_ceiling = input_floor + sensitivity

peak = 0
while True:
    mic.record(samples, len(samples))
    magnitude = normalized_rms(samples)
    print((magnitude),)

    c = log_scale(constrain(magnitude, input_floor, input_ceiling),
                  input_floor, input_ceiling, 0, NUM_PIXELS)

    pixels.fill(0)
    for i in range(NUM_PIXELS):
        if i < c:
            pixels[i] = volume_color(i)
        if c >= peak:
            peak = min(c, NUM_PIXELS - 1)
        elif peak > 0:
            peak = peak - 1
        if peak > 0:
            pixels[int(peak)] = PEAK_COLOR
    pixels.show()