Frequency estimation

estimate_frequency.py

import pyaudio
import numpy as np
import scipy.signal
import time
import sounddevice as sd

RATE = 44100
CHUNK = 2048
DURATION = 10  # seconds to record

def record_audio(duration, rate, chunk):
    p = pyaudio.PyAudio()
    stream = p.open(format=pyaudio.paInt16,
                    channels=1,
                    rate=rate,
                    input=True,
                    frames_per_buffer=chunk)

    print("Recording...")
    frames = []
    for _ in range(0, int(rate / chunk * duration)):
        data = stream.read(chunk)
        frames.append(np.frombuffer(data, dtype=np.int16))
    print("Done.")
    
    stream.stop_stream()
    stream.close()
    p.terminate()

    audio = np.hstack(frames)
    return audio

# Estimate frequency using autocorrelation
def estimate_frequency(signal, rate):
    # Apply a Hamming window
    signal = signal * np.hamming(len(signal))

    # Autocorrelation
    corr = np.correlate(signal, signal, mode='full')
    corr = corr[len(corr)//2:]

    # Find first minimum then maximum after it
    d = np.diff(corr)
    start = np.where(d > 0)[0][0]

    peak = np.argmax(corr[start:]) + start
    fundamental_freq = rate / peak
    return fundamental_freq

def play_tone(frequency, duration=2.0, rate=44100):
    t = np.linspace(0, duration, int(rate * duration), False)
    tone = 0.5 * np.sin(2 * np.pi * frequency * t)
    sd.play(tone, rate)
    sd.wait()

if __name__ == "__main__":
    audio = record_audio(DURATION, RATE, CHUNK)
    freq = estimate_frequency(audio, RATE)
    print(f"Estimated frequency: {freq:.2f} Hz")
    play_tone(freq, duration=2.0)