Effect of temporal modulation reduction on spectral contrasts in speech

Area of Science:

• Acoustics
• Speech Processing
• Psychoacoustics

Background:

• Temporal modulation reduction impacts speech perception.
• Spectral contrasts are crucial for understanding speech in noise.

Purpose of the Study:

• Investigate the effect of temporal modulation reduction on spectral contrasts.
• Quantify spectral contrast reduction using a spectral modulation transfer function (SMTF).
• Evaluate the perceptual impact on speech reception threshold (SRT) in noise.

Main Methods:

• Developed and utilized a spectral modulation transfer function (SMTF) to measure spectral ripple transfer.
• Applied uniform temporal modulation reduction across 24 1/4-oct bands.
• Measured SRT in noise for sentences with reduced spectral contrasts in ten normal-hearing subjects.

Main Results:

• Uniform temporal modulation reduction led to a corresponding uniform reduction in spectral modulations.
• Temporal high-pass filtering's effect on SRT was fully explained by spectral contrast reduction.
• Temporal low-pass filtering's effect on SRT could not be conclusively linked to spectral contrast reduction.

Conclusions:

• Spectral contrast reduction is a key factor in speech intelligibility changes due to temporal processing.
• High-pass temporal filtering significantly impacts speech perception via spectral contrast reduction.
• The relationship between low-pass temporal filtering and spectral contrast reduction requires further investigation.