Generating a sine wave sound in python

Question

I've been trying to generate a sine wave using the following code and playing it thought my speakers, but it sounds horrible. Anyone knows why? It does not sound like a sine wave.

       dur = int(FS * float(duration) / 1000)
       for i in range(dur):
         a = frequency * i * 2 * math.pi / FS
         y = math.sin(a)
         outbuf[i] = y * 0.2

p = pyaudio.PyAudio()
stream = p.open(format=pyaudio.paFloat32, channels=1, rate=44100, output=True)
stream.write(outbuf)
stream.stop_stream()
stream.close()
p.terminate()

play_sound("sine", 1000, 1, 1000)

Answer 1

the audio buffer must be packed into binary, for python3 use b''.join(struct.pack also simplified the sin curve synthesis by moving the angle theta increment constant to outside of the loop

import pyaudio
import numpy as np
import math
import struct

FS = 44100  #  frames per second, samples per second or sample rate

def play_sound(type, frequency, volume, duration):

   generate_sound(type, frequency, volume, duration)

def generate_sound(type, frequency, volume, duration):

    outbuf = np.random.normal(loc=0, scale=1, size=int(float(duration / 1000.0)*FS))

    if type == "sine":
        dur = int(FS * float(duration / 1000.0))
        theta = 0.0
        incr_theta = frequency * 2 * math.pi / FS # frequency increment normalized for sample rate
        for i in range(dur):
            outbuf[i] = volume * math.sin(theta)
            theta += incr_theta

    p = pyaudio.PyAudio()
    stream = p.open(format=pyaudio.paFloat32, channels=1, rate=FS, output=True)
    data = b''.join(struct.pack('f', samp) for samp in outbuf) # must pack the binary data
    stream.write(data)
    stream.stop_stream()
    stream.close()
    p.terminate()

play_sound("sine", 220, 0.8, 1000)  #  duration in milliseconds

above python executes just fine on my Ubuntu laptop across various release including ubuntu 20.04 ... however below is output to terminal when I run above code ... just ignore below messages sadly those are normal

python generate_sin_wave_sound.py 

ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm_route.c:869:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:869:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:869:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:869:(find_matching_chmap) Found no matching channel map
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
ALSA lib pcm_oss.c:377:(_snd_pcm_oss_open) Unknown field port
ALSA lib pcm_oss.c:377:(_snd_pcm_oss_open) Unknown field port
ALSA lib pcm_usb_stream.c:486:(_snd_pcm_usb_stream_open) Invalid type for card
ALSA lib pcm_usb_stream.c:486:(_snd_pcm_usb_stream_open) Invalid type for card
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock