freq_examples_1.py

import numpy as np
import matplotlib.pyplot as plt
import scipy.signal

SAMPLE_RATE = 44100
DURATION_SEC = 2
FREQ1 = 1000
FREQ2 = 1050
T = 1 / SAMPLE_RATE

n_samples = SAMPLE_RATE * DURATION_SEC
t = np.arange(n_samples) / T
x1 = np.cos(2 * np.pi * FREQ1 * T * np.arange(n_samples))
x2 = np.cos(2 * np.pi * FREQ2 * T * np.arange(n_samples) + 2 * np.pi / 3)

LIMIT = 1000
#plt.plot(t[:LIMIT], x1[:LIMIT], label=f"{FREQ1} Hz")
#plt.plot(t[:LIMIT], x2[:LIMIT], label=f"{FREQ2} Hz")
s = x1 + 0.01 * x2
# plt.plot(t[:LIMIT], s[:LIMIT], label=f"{FREQ1} Hz, {FREQ2} Hz")
# plt.legend()
# plt.show()

# We do the FFT and see
N = 1024
S = np.fft.fft(scipy.signal.windows.hamming(N) * s[:N])
#S = np.fft.fft(s[:N])
plt.stem(20*np.log10(np.abs(S)))
plt.show()