Add Noise to Speech at Specific SNR Levels

Add noise to speech at specific signal-to-noise ratio levels.

To see how soundpy implements this, see soundpy.dsp.add_backgroundsound.

Let’s import soundpy, and ipd for playing audio data

import soundpy as sp
import IPython.display as ipd

Define the speech and noise data samples

I will use speech and noise data from the soundpy repo.

Designate path relevant for accessing audiodata

sp_dir = '../../../'

Speech sample:

speech_sample = '{}audiodata/python.wav'.format(sp_dir)
speech_sample = sp.utils.string2pathlib(speech_sample)
# as pathlib object, can do the following:
word = speech_sample.stem
word

Out:

'python'

Noise sample:

noise_sample = '{}audiodata/background_samples/cafe.wav'.format(sp_dir)
noise_sample = sp.utils.string2pathlib(noise_sample)
# as pathlib object, can do the following:
noise = noise_sample.stem
noise

Out:

'cafe'

Hear Clean Speech

I’m using a higher sample rate here as calculating SNR performs best upwards of 44100 Hz.

sr = 44100
s, sr = sp.loadsound(speech_sample, sr = sr)
ipd.Audio(s,rate=sr)

Hear Noise

n, sr = sp.loadsound(noise_sample, sr = sr)
ipd.Audio(n,rate=sr)

Hear Signal-to-Noise Ratio 20

noisyspeech_20snr, snr20 = sp.dsp.add_backgroundsound(
    speech_sample,
    noise_sample,
    sr = sr,
    snr = 20)
ipd.Audio(noisyspeech_20snr,rate=sr)

Out:

/home/airos/Projects/github/a-n-rose/Python-Sound-Tool/soundpy/dsp.py:769: UserWarning:
Warning: `soundpy.dsp.clip_at_zero` found no samples close to zero. Clipping was not applied.

  warnings.warn(msg)

snr20 is simply the measured SNR post adjustment fo the noise signal. This is useful to check that the indicated snr is at least close to the resulting snr.

snr20

Out:

19.999968503067556

Hear Signal-to-Noise Ratio 5

noisyspeech_5snr, snr5 = sp.dsp.add_backgroundsound(
    speech_sample,
    noise_sample,
    sr = sr,
    snr = 5)
ipd.Audio(noisyspeech_5snr,rate=sr)

snr5

Out:

5.000011686690687

Visualize the Audio Samples

See Clean Speech (raw signal)

sp.plotsound(speech_sample, feature_type='signal',
               sr = sr, title = 'Speech: ' + word.upper(),
               subprocess=True)

Out:

/home/airos/Projects/github/a-n-rose/Python-Sound-Tool/soundpy/feats.py:117: UserWarning: Due to matplotlib using AGG backend, cannot display plot. Therefore, the plot will be saved here: current working directory
  warnings.warn(msg)

See Clean Speech (stft)

sp.plotsound(speech_sample, feature_type='stft',
               sr = sr, title = 'Speech: ' + word.upper(),
               subprocess=True)

Out:

/home/airos/Projects/github/a-n-rose/Python-Sound-Tool/soundpy/feats.py:117: UserWarning: Due to matplotlib using AGG backend, cannot display plot. Therefore, the plot will be saved here: current working directory
  warnings.warn(msg)

---

sp.plotsound(noise_sample, feature_type='signal',
               title = 'Noise: ' + noise.upper(), subprocess=True)

---

sp.plotsound(noise_sample, feature_type='stft',
               title = 'Noise: ' + noise.upper(), subprocess=True)

Out:

/home/airos/Projects/github/a-n-rose/Python-Sound-Tool/soundpy/feats.py:117: UserWarning: Due to matplotlib using AGG backend, cannot display plot. Therefore, the plot will be saved here: current working directory
  warnings.warn(msg)

See Noisy Speech: SNR 20 (raw signal)

sp.plotsound(noisyspeech_20snr, sr = sr, feature_type = 'signal',
               title = '"{}" with {} noise at SNR 20'.format(word.upper(), noise.upper()),
               subprocess=True)

See Noisy Speech: SNR 20 (stft)

sp.plotsound(noisyspeech_20snr, sr = sr, feature_type = 'stft',
               title = '"{}" with {} noise at SNR 20'.format(word.upper(), noise.upper()),
               subprocess=True)

Out:

/home/airos/Projects/github/a-n-rose/Python-Sound-Tool/soundpy/feats.py:117: UserWarning: Due to matplotlib using AGG backend, cannot display plot. Therefore, the plot will be saved here: current working directory
  warnings.warn(msg)

See Noisy Speech: SNR 5 (raw signal)

sp.plotsound(noisyspeech_5snr, sr = sr, feature_type = 'signal',
               title = '"{}" with {} noise at SNR 5'.format(word.upper(), noise.upper()),
               subprocess=True)

See Noisy Speech: SNR 5 (stft)

sp.plotsound(noisyspeech_20snr, sr = sr, feature_type = 'stft',
               title = '"{}" with {} noise at SNR 5'.format(word.upper(), noise.upper()),
               subprocess=True)

Out:

/home/airos/Projects/github/a-n-rose/Python-Sound-Tool/soundpy/feats.py:117: UserWarning: Due to matplotlib using AGG backend, cannot display plot. Therefore, the plot will be saved here: current working directory
  warnings.warn(msg)

Make Combined Sound Longer

Pad Speech and Set Total Length

noisyspeech_20snr, snr20 = sp.dsp.add_backgroundsound(
    speech_sample,
    noise_sample,
    sr = sr,
    snr = 20,
    pad_mainsound_sec = 1,
    total_len_sec = 4)

Out:

/home/airos/Projects/github/a-n-rose/Python-Sound-Tool/soundpy/dsp.py:769: UserWarning:
Warning: `soundpy.dsp.clip_at_zero` found no samples close to zero. Clipping was not applied.

  warnings.warn(msg)

ipd.Audio(noisyspeech_20snr,rate=sr)

sp.plotsound(noisyspeech_20snr, sr = sr, feature_type = 'signal',
               title = '"{}" with {} noise at SNR 20'.format(word.upper(), noise.upper()),
               subprocess=True)

Make Combined Sound Shorter

Set Total Length

noisyspeech_20snr, snr20 = sp.dsp.add_backgroundsound(
    speech_sample,
    noise_sample,
    sr = sr,
    snr = 20,
    total_len_sec = 0.75)

Out:

/home/airos/Projects/github/a-n-rose/Python-Sound-Tool/soundpy/dsp.py:531: UserWarning: The length of `audio_main` and `pad_mainsound_sec `exceeds `total_len_sec`. 5018 samples from `audio_main` will be cut off in the `combined` audio signal.
  warnings.warn('The length of `audio_main` and `pad_mainsound_sec `'+\
/home/airos/Projects/github/a-n-rose/Python-Sound-Tool/soundpy/dsp.py:769: UserWarning:
Warning: `soundpy.dsp.clip_at_zero` found no samples close to zero. Clipping was not applied.

  warnings.warn(msg)

ipd.Audio(noisyspeech_20snr,rate=sr)

sp.plotsound(noisyspeech_20snr, sr = sr, feature_type = 'signal',
               title = '"{}" with {} noise at SNR 20'.format(word.upper(), noise.upper()),
               subprocess=True)

Out:

/home/airos/Projects/github/a-n-rose/Python-Sound-Tool/soundpy/feats.py:117: UserWarning: Due to matplotlib using AGG backend, cannot display plot. Therefore, the plot will be saved here: current working directory
  warnings.warn(msg)

Wrap the Background Sound

noisyspeech_20snr, snr20 = sp.dsp.add_backgroundsound(
    speech_sample,
    noise_sample,
    sr = sr,
    snr = 20,
    wrap = True,
    pad_mainsound_sec = 2,
    total_len_sec = 5)

Out:

/home/airos/Projects/github/a-n-rose/Python-Sound-Tool/soundpy/dsp.py:769: UserWarning:
Warning: `soundpy.dsp.clip_at_zero` found no samples close to zero. Clipping was not applied.

  warnings.warn(msg)

ipd.Audio(noisyspeech_20snr,rate=sr)

sp.plotsound(noisyspeech_20snr, sr = sr, feature_type = 'signal',
               title = '"{}" with {} noise at SNR 20'.format(word.upper(), noise.upper()),
               subprocess=True)

Out:

/home/airos/Projects/github/a-n-rose/Python-Sound-Tool/soundpy/feats.py:117: UserWarning: Due to matplotlib using AGG backend, cannot display plot. Therefore, the plot will be saved here: current working directory
  warnings.warn(msg)