title: How to remove PyAudio errors?
body: <p>I am trying out a solution to an accepted question that demonstrates how to create a beep with PyAudio. Strangely I see quite a lot of errors. Unfortunately I've never sent any audio data programatically to a sound card so I've no idea about how to get rid of the errors. The Internet was not very helpful, so could you provide me with some advice? Thank you!</p>
  
  <p>Here's a short program that produces the beep as provided by an answer here on StackOverflow:</p>
  
  <pre><code>#!/usr/bin/python3
  
  import math
  
  from pyaudio import PyAudio # sudo apt-get install python{,3}-pyaudio
  
  def sine_tone(frequency:float, duration:float, volume:int = 1, sampleRate:int = 22050):
      n_samples = int(sampleRate * duration)
      restframes = n_samples % sampleRate
  
      p = PyAudio()
      stream = p.open(format=p.get_format_from_width(1), # 8bit
                      channels=1, # mono
                      rate=sampleRate,
                      output=True)
      s = lambda t: volume * math.sin(2 * math.pi * frequency * t / sampleRate)
      samples = (int(s(t) * 0x7f + 0x80) for t in range(n_samples))
      if duration &lt; 1:
          stream.write(bytes(bytearray(samples)))
      else:
          for buf in zip(*[samples]*sampleRate): # write several samples at a time
              stream.write(bytes(bytearray(buf)))
  
      # fill remainder of frameset with silence
      stream.write(b'\x80' * restframes)
  
      stream.stop_stream()
      stream.close()
      p.terminate()
  #
  
  sine_tone(500, 1)
  </code></pre>
  
  <p>This will result in the following output lines that are all sent to STDERR:</p>
  
  <pre><code>ALSA lib pcm_dmix.c:1052:(snd_pcm_dmix_open) unable to open slave
  ALSA lib pcm_dmix.c:1052:(snd_pcm_dmix_open) unable to open slave
  ALSA lib pcm.c:2495:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
  ALSA lib pcm.c:2495:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
  ALSA lib pcm.c:2495:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
  ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
  ALSA lib pcm_dmix.c:1052:(snd_pcm_dmix_open) unable to open slave
  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 4294967295, skipping unlock
  JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for 4294967295, skipping unlock
  </code></pre>
  
  <p>Why are msgs sent to STDERR, what do they mean and how can I get rid of them (as sound seems to be played as expected)?</p>