Durations required to distinguish noise and tone: Effects of noise bandwidth and frequency

Armin Taghipour,Brian C J Moore,Bernd Edler

doi:10.1121/1.4945702

Abstract

Perceptual audio coders exploit the masking properties of the human auditory system to reduce the bit rate in audio recording and transmission systems; it is intended that the quantization noise is just masked by the audio signal. The effectiveness of the audio signal as a masker depends on whether it is tone-like or noise-like. The determination of this, both physically and perceptually, depends on the duration of the stimuli. To gather information that might improve the efficiency of perceptual coders, the duration required to distinguish between a narrowband noise and a tone was measured as a function of center frequency and noise bandwidth. In experiment 1, duration thresholds were measured for isolated noise and tone bursts. In experiment 2, duration thresholds were measured for tone and noise segments embedded within longer tone pulses. In both experiments, center frequencies were 345, 754, 1456, and 2658 Hz and bandwidths were 0.25, 0.5, and 1 times the equivalent rectangular bandwidth of the auditory filter at each center frequency. The duration thresholds decreased with increasing bandwidth and with increasing center frequency up to 1456 Hz. It is argued that the duration thresholds depended mainly on the detection of amplitude fluctuations in the noise bursts.

Highlights

Perceptual audio coders (Bosi et al, 1997; Brandenburg and Bosi, 1997; Brandenburg and Stoll, 1994; Stoll and Brandenburg, 1992) exploit the masking properties of the human auditory system to reduce the bit rate of digital recording and transmission systems; the audio signal is treated as the masker and quantization noise as the “probe” that is to be masked at the output of the decoder
The audio signal is split into brief segments, called “frames.” The frame length may be fixed or it can vary according to the characteristics of the signal
The results suggest that duration thresholds are determined by how much the envelope fluctuates during the stimulus and by the rapidity of the fluctuation; rapid fluctuations are harder to detect than slow fluctuations, consistent with temporal modulation transfer functions (Dau et al, 1997; Viemeister, 1979; Viemeister and Plack, 1993)

Summary

Introduction

Perceptual audio coders (Bosi et al, 1997; Brandenburg and Bosi, 1997; Brandenburg and Stoll, 1994; Stoll and Brandenburg, 1992) exploit the masking properties of the human auditory system to reduce the bit rate of digital recording and transmission systems; the audio signal is treated as the masker and quantization noise as the “probe” that is to be masked at the output of the decoder. The audio signal is split into brief segments, called “frames.” The frame length may be fixed or it can vary according to the characteristics of the signal. The signal is filtered into a number of adjacent frequency bands called subbands. The greater the number of bits, the lower is the quantization noise relative to the audio signal. The most efficient a)Portions of this study were presented in Taghipour et al (2013) and Taghipour et al (2014)

Methods

Findings

Discussion

Conclusion