This is a 3rd year bioengineering project at Imperial College London that is researching into the psychoacoustic effects of distortion induced by transducers. We explore how a transducer can affect the amplitude, phase, group delay and induce new frequencies into an input signal. We determine the psychoacoustic perception of these effects and quantify them using novel Acoustic Quality Metrics. Finaly, we aim to remove all the effects of a transducer by creating an inverse filter.

• rlogbarkrangedv2.m
  • Calculates the log mean at certain points given by the bark scale over a rectangular window with a frequency dependent width
  • Outputs the points and the frequency spacing of the points
  • The ouput frequency range can be optionally specified
  • Note: this function replaces rlogbark.m and rlogbarkranged.m. If any files exist using either of these functions please replace them with this function.
• rgeobarkrangedv2.m
  • Calculates the geometric mean at certain points given by the bark scale over a rectangular window with a frequency dependent width
  • Outputs the points and the frequency spacing of the points
  • The ouput frequency range can be optionally specified
  • Note: this function replaces rgeobark.m and rgeobarkranged.m. If any files exist using either of these functions please replace them with this function.

• alpaToSigma.m
  • Calculates sigma value for inverse filter warped IIR transfer function
• ampegif.m
  • Example file for finding inverse filter with all methods
  • See https://soundwoofer.com/Library/Index for impulse response used (freely available).
• ashdownif.m
  • Example file for finding inverse filter with all methods
  • See https://soundwoofer.com/Library/Index for impulse response used (freely available).
• barkwarp.m
  • Calculates lambda value based on sampling frequency
• inverseFilter.m
  • Function for finding minimum phase and all-pass inverse filter components in the frequency domain
• inverseFilterv3.m
  • New version of function for finding minimum phase and all-pass inverse filter components in the frequency domain
• inverseFilterTime.m
  • Finds the inverse filter in the time domain method using the method in http://www.aes.org/e-lib/browse.cfm?elib=12098.
• if_test.m
  • Example file for finding inverse filter with all methods
  • Uses impulse response provided at start of project (IR19061314201696-1.wav)
• warpedFIR.m
  • Applies a warped FIR filter
• warpedIIR.m
  • Applies a warped IIR filter
• warpImpulseResponse.m
  • Warps the impulse response so that warped FIR or warped IIR filter coefficients can be found

• AutoPeak.m
  • Calculates peak values of first three harmonics
• HarmonicFilt.m
  • Sections harmonics from a signal to be displayed
• Harmonics.m
  • Main function that plots graph of each harmonic and plots total harmonic distortion.
• MidFinder.m
  • Finds the midpoints between harmonics.
• PeakRemover.m
  • Remove harmonics from a signal.
• calculateTHD.m
  • Function that calcuates the total harmonic distortion of an input signal.
• removeNoise.m
  • Function that remove background noise present in the signal.

• GDAQM.m
  • Function that determines a score for the group delay distortion of a signal.
• Blauert.mat
  • Audability threshold for group delay calculation.

• AmpAQM.m
  • Function that determines a score for the amplitude distortion of a signal.
• toleranceTube.mat
  • Limits for tolerance tube used in AmpAQM.m

• Prof Guy-Bart Stan
• Mr Christophe Hermans

• Megan Allerton
• Krithika Balaji
• Hongzhang (Tommy) Chen
• Marcella Iswanto
• Shivali Jain
• Gabrielle Johnston
• Alexander McKinnon