Record audio and plot spectrogram in Python

. Record audio and plot spectrogram in Python.md

Record audio and plot spectrogram in Python

Below is a Python script which demonstrates how to record audio in Python, calculate a spectrogram, and plot the spectrogram, followed by a few usage examples (me playing the opening bars of "Majorca" by Albeniz, and me whistling a major triad and then some random notes).

spectrogram.py

import sounddevice as sd
from scipy import signal
import matplotlib.pyplot as plt
import numpy as np
import os

def record_audio(duration=3, fs=44.1e3, playback=True):
    print("Starting recording...")
    x = sd.rec(int(duration * fs), fs, channels=1, blocking=True)
    print("Finished recording")
    if playback:
        sd.play(x, fs, blocking=True)
    return x.ravel()
    
def spectrogram(
    x, fs=44.1e3, fs_spec=60, f_lo=20, f_hi=20e3, freqs_per_octave=60,
    n_overlap=1
):
    f_log2 = np.arange(np.log2(f_lo), np.log2(f_hi), 1/freqs_per_octave)
    f = np.power(2, f_log2)

    sample_interval = fs / fs_spec
    n_per_sample = int(sample_interval * (1 + n_overlap))
    n_samples = int(
        (x.size - (n_per_sample - sample_interval)) // int(sample_interval)
    )

    t = np.arange(n_samples) / fs_spec
    window = signal.windows.hamming(n_per_sample)
    spectrogram_array = np.zeros([f.size, n_samples])

    for i in range(n_samples):
        start = int(i * sample_interval)
        end = start + n_per_sample
        x_chunk = x[start:end] * window
        _, h = signal.freqz(x_chunk, worN=f, fs=fs)
        spectrogram_array[:, i] = np.abs(h)
    
    return t, f, spectrogram_array

def plot_spectrogram(
    t, f, spectrogram_array, fs_spec=30, name="Spectrogram", dir_name="Images"
):
    plt.figure(figsize=[8, 6])
    plt.pcolormesh(t, np.log2(f), spectrogram_array)
    plt.xlabel("Time (s)")
    plt.ylabel("$\log_{2}$(frequency)")
    plt.title(name)
    if not os.path.isdir(dir_name): os.makedirs(dir_name)
    plt.savefig("{}/{}.png".format(dir_name, name))
    plt.close()

if __name__ == "__main__":
    x = record_audio(5, playback=True)
    t, f, sa = spectrogram(x, n_overlap=3)
    plot_spectrogram(t, f, sa)

z1_Spectrogram guitar Mallorca.png

z2_Spectrogram whistle triad.png

z3_Spectrogram whistle random.png