How do I generate a sine wave using Python?

Question

I'm trying to generate a sine wave of a given frequency for a given duration and then write it into a .wav file. I'm using numpy's sin function and scipy's wavfile function. I'm getting a weird sound that is definitely not a sine wave.

import numpy as np
from scipy.io import wavfile

fs = 44100

f = int(raw_input("Enter fundamental frequency: "))
t = float(raw_input("Enter duration of signal (in seconds): "))

samples = np.arange(t * fs)

signal = np.sin(2 * np.pi * f * samples)

signal *= 32767

signal = np.int16(signal)

wavfile.write(str(raw_input("Name your audio: ")), fs, signal)

Any help would be appreciated. Have I made some fundamentally incorrect assumption about sine waves or something?

What happens if you try `samples = np.arange(t * fs) / fs`? – Paul Panzer Dec 31 '17 at 14:11 — Paul Panzer, Dec 31 '17 at 14:11

score 15 · Answer 1 · answered Dec 31 '17 at 14:12

15

Change

samples = np.arange(t * fs)

to

samples = np.linspace(0, t, int(fs*t), endpoint=False)

(This assumes that fs*t results in an integer value.)

Or, as Paul Panzer suggests in a comment,

samples = np.arange(t * fs) / fs

Your samples was just the sequence of integers 0, 1, 2, ... fs*t. Instead, you need the actual time values (in seconds) of the samples.

answered Dec 31 '17 at 14:12

Warren Weckesser

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I think mine is marginally more precise (in case `fs*t` is not integer). – Paul Panzer Dec 31 '17 at 14:21
Yeah, now I understand! The samples variable has to be in seconds and not samples. Thank you! – Badrinarayan Rammohan Jan 01 '18 at 05:28

score 7 · Answer 2 · answered Apr 28 '22 at 16:31

A simplified approach:

cycles = 2 # how many sine cycles
resolution = 25 # how many datapoints to generate

length = np.pi * 2 * cycles
my_wave = np.sin(np.arange(0, length, length / resolution))

Generates:

[ 0.      0.4818  0.8443  0.998   0.9048  0.5878  0.1253 -0.3681 -0.7705
 -0.9823 -0.9511 -0.6845 -0.2487  0.2487  0.6845  0.9511  0.9823  0.7705
  0.3681 -0.1253 -0.5878 -0.9048 -0.998  -0.8443 -0.4818]

Note: Leaving this answer here despite not addressing sine wave for audio generation, since I found that for my application it was more intuitive to only parameterise length of the wave and number of datapoints generated, as opposed to fundamental frequency and duration in seconds.

score 4 · Answer 3 · answered Sep 12 '21 at 14:47

Use this and set the parameters as you want

start_time = 0
end_time = 1
sample_rate = 1000
time = np.arange(start_time, end_time, 1/sample_rate)
theta = 0
frequency = 100
amplitude = 1
sinewave = amplitude * np.sin(2 * np.pi * frequency * time + theta)
figure(figsize=(20, 6), dpi=80)
plt.plot(sinewave)

score 3 · Answer 4 · answered Dec 31 '17 at 14:13

3

You are mixing sample value and length! Try:

samples = np.linspace(0, t, t * fs)

Another detail: you don't need the str around raw_input.

answered Dec 31 '17 at 14:13

grovina

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How do I generate a sine wave using Python?

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