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mundya/frequency_masking.py

Created February 9, 2015 20:13
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frequency_masking.py
"""Frequency masking experiment for COMP28512.
(C) University of Manchester 2015
Author: Andrew Mundy
"""
from __future__ import print_function
import comp28512_utils
from IPython import display
from matplotlib import pyplot as plt
import numpy as np
import os.path
from scipy.io import wavfile
import tempfile
def generate_sound_files(fs=44.1*10**3, full_duration=4.0, signal_duration=2.0,
signal_start=2.0, f_mask=1000.0, a_mask=0.5,
n_tests=10, path=None):
"""Generate the audio files for the frequency masking experiment.
Parameters
----------
fs : float
Sampling frequency.
full_duration : float
Full duration of each sample.
signal_duration : float
Duration of the non-silent part of each sample.
signal_start : float
f_mask : float
Frequency of the masking signal.
a_mask : float
Amplitude of the masking signal.
n_tests : int
Number of tests to make.
path : string or None
Full path of the directory to write the tests into. If None then a new
temporary directory will be created.
Returns
-------
list
[(frequency, [(AdB, path of wave file)])]
"""
# Get the directory
if path is None:
path = tempfile.mkdtemp(suffix="comp28512")
# Signal samples
signal_ns = np.arange(fs * (signal_start + signal_duration),
dtype=np.uint32)
sample_ns = np.arange(fs * signal_start,
fs * (signal_start + signal_duration),
dtype=np.uint32)
# Generate the masking signal
masker = np.zeros(full_duration * fs)
masker[signal_ns] = a_mask * np.sin(2*np.pi*signal_ns*f_mask/fs)
# Signal dictionary
wavs = list()
# For each sample frequency
for k in range(1, n_tests + 1):
# Get the test frequency
f_test = f_mask + 100*(2*k - 9) # Magic!
# Prepare the list of wavs
f_wavs = list()
# For various power levels
for m in range(1, n_tests + 1):
adb = (m - 10.0)*6
amplitude = a_mask * 10**(adb / 20)
# Generate the sound data, first copy the masking signal
y = np.zeros(masker.size)
y[:] = masker[:]
y[sample_ns] += amplitude * np.sin(2*np.pi*f_test*sample_ns/fs)
y_data = np.int16(y * (2.0**15 - 1))
# Write to file, add to the list of wav files
fn = os.path.join(path, "{},{}.wav".format(k, m))
wavfile.write(fn, fs, y_data)
f_wavs.append((adb, fn))
wavs.append((f_test, f_wavs))
return wavs
def run_experiment(*args, **kwargs):
"""Run the frequency masking experiment in an IPython notebook.
Parameters
----------
fs : float
Sampling frequency.
full_duration : float
Full duration of each sample.
signal_duration : float
Duration of the non-silent part of each sample.
signal_start : float
f_mask : float
Frequency of the masking signal.
a_mask : float
Amplitude of the masking signal.
n_tests : int
Number of tests to make.
path : string or None
Full path of the directory to write the tests into. If None then a new
temporary directory will be created.
"""
display.display_html("<p>Generating audio...</p>", raw=True)
# Generate the samples given the parameters
samples = generate_sound_files(*args, **kwargs)
display.display_html("<p>The following experiment will play a series of "
"audio samples, you should indicate whether you hear "
"a change occur during a sample. <b>Ensure you are "
"wearing headphones.</b></p>", raw=True)
# Are you sitting comfortably?
raw_input("Press return to start:")
# Then I'll begin
# Run through the experiment
display.clear_output()
thresh = np.zeros(len(samples))
freqs = np.array([f for (f, _) in samples])
for n, (freq, tests) in enumerate(samples):
for (adb, wav) in tests:
display.clear_output()
print("{:4.0f} Hz at {:4.1f}dB".format(freq, adb))
play_audio(wav)
inp = None
while inp not in ["y", "n"]:
inp = raw_input("Did you hear any change during the sample? "
"(y|n)")
if inp == "y":
thresh[n] = adb
break
# Plot the results
fig, ax = plt.subplots(1)
ax.plot(freqs, thresh)
ax.set_xlabel("Frequency of masked signal / Hz")
ax.set_ylabel("Threshold / Amplitude relative to masking signal")
ax.set_xlim(np.min(freqs), np.max(freqs))
ax.set_ylim(-55.0, 0)
ax.grid(True)
# Return the results
return freqs, thresh
def play_audio(filename):
display.display_html(display.HTML(
"<p><audio autoplay controls>"
"<source src=\"{}\" type=\"audio/wav\" />"
"Please listen to {}"
"</audio></p>".format(comp28512_utils.get_audio_from_file(filename),
filename))
)
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