Release from masking of low-frequency complex tones by high-frequency complex tone cue bands

Abstract

This study investigated the influence of high-frequency cue bands on the detection and discrimination of low-frequency target bands presented in a 3000-Hz low-pass noise masker. Target and cue bands were complex tones with 80-Hz spacing. The cue band consisted of 60 components starting at 4000 Hz; targets consisted of four components starting at different frequencies (500, 700, 1000, 1200, and 1500 Hz). Targets were presented with different durations within the 500-ms masker; target and cue bands had a common on- and offset. Presentation of the high-frequency complex tone significantly enhanced both the discrimination and detection thresholds by 2–3 dB.

The Influence of High-Frequency Envelope Information on Low-Frequency Vowel Identification in Noise

“…In the first experiment, the low-frequency part of the stimulus was either intact low-frequency speech (LFS) or a version of the logatome that was generated with linear predictive coding (LPC) as shown in Fig 1 . LPC-vocoding was chosen to relate to findings from [ 11 , 15 , 19 ] where the stimuli were harmonic complex tones. The LFS was generated by low-pass filtering the intact speech with an 8 th -order Butterworth filter with a cutoff-frequency of 2.5 kHz.…”

“…In [ 15 ], detection and discrimination thresholds of low-frequency complex tones (designed as “stylized formants”) were found to improve significantly in the presence of an additional high-frequency cue band. This band provided information on temporal on- and offsets as well as periodicity of the low-frequency complex tone, but carried no other information.…”

“…Based on results by [ 15 – 17 ] it can be hypothesized that periodicity information presented in a co-signal from a high-frequency region supports the perception of speech parts with the same periodicity in another frequency region. Such a hypothetical mechanism would be conceptually similar to the strobed integration stage as proposed by [ 18 ].…”

“…In experiment 1, the experimental design of [ 15 ] was extended by using speech stimuli instead of complex tones and vowel identification instead of a psychoacoustic discrimination task. This was done to test if a hypothesized strobed integration, as proposed in [ 18 ], due to common periodicity [ 11 , 17 , 19 ] is in principle possible for stimuli that are similar to the vowels in natural speech since the research hypothesis cannot be tested with unmodified natural speech.…”

“…This was done to test if a hypothesized strobed integration, as proposed in [ 18 ], due to common periodicity [ 11 , 17 , 19 ] is in principle possible for stimuli that are similar to the vowels in natural speech since the research hypothesis cannot be tested with unmodified natural speech. Earlier studies [ 11 , 15 , 17 ] used stimuli that were not natural, e.g. complex tones or synthesized vowels.…”