The dominant region for the pitch of complex tones with low fundamental frequencies

Effect of inharmonicity on pitch perception and subjective tuning of piano tones

The consensus in piano tuning philosophy explains the stretched tuning scale by the inharmonicity of piano strings. This study aimed to examine how variable inharmonicity influences the result of the piano tuning process, compare the tuning curves of aurally tuned pianos with the curves derived from subjective octave enlargement experiments, and evaluate whether the pitches of inharmonic or harmonic versions of the same tone are perceived differently. In addition, the influence of strings of other piano keys on the measured inharmonicity of a single piano string was investigated. The inharmonicity of all individual strings was measured on a Steinway D grand piano. Variable inharmonicity was implemented by additive synthesis with frequency-adjusted sinusoidal partials. Fifteen piano tuners and 18 orchestra musicians participated in the experiments. The results indicate that the inharmonic piano tones produced a keyboard tuning curve similar to the Railsback curve and differed significantly from the harmonic counterpart. The inharmonic tuning curve was reminiscent of the subjective octave enlargement curve. Inharmonic tone pitches were perceived to be higher than harmonic tones up to C ♯ 7. The covibrating strings of the other keys did not exhibit any meaningful effect on the measured inharmonicity of a single string of the played key.

Effect of lowest harmonic rank on fundamental-frequency difference limens varies with fundamental frequency

This study investigated the relationship between fundamental frequency difference limens (F0DLs) and the lowest harmonic number present over a wide range of F0s (30-2000 Hz) for 12-component harmonic complex tones that were presented in either sine or random phase. For fundamental frequencies (F0s) between 100 and 400 Hz, a transition from low (∼1%) to high (∼5%) F0DLs occurred as the lowest harmonic number increased from about seven to ten, in line with earlier studies. At lower and higher F0s, the transition between low and high F0DLs occurred at lower harmonic numbers. The worsening performance at low F0s was reasonably well predicted by the expected decrease in spectral resolution below about 500 Hz. At higher F0s, the degradation in performance at lower harmonic numbers could not be predicted by changes in spectral resolution but remained relatively good (<2%-3%) in some conditions, even when all harmonics were above 8 kHz, confirming that F0 can be extracted from harmonics even when temporal envelope or fine-structure cues are weak or absent.

Effect of harmonic rank on sequential sound segregation

The ability to segregate sounds from different sound sources is thought to depend on the perceptual salience of differences between the sounds, such as differences in frequency or fundamental frequency (F0). F0 discrimination of complex tones is better for tones with low harmonics than for tones that only contain high harmonics, suggesting greater pitch salience for the former. This leads to the expectation that the sequential stream segregation (streaming) of complex tones should be better for tones with low harmonics than for tones with only high harmonics. However, the results of previous studies are conflicting about whether this is the case. The goals of this study were to determine the effect of harmonic rank on streaming and to establish whether streaming is related to F0 discrimination. Thirteen young normal-hearing participants were tested. Streaming was assessed for pure tones and complex tones containing harmonics with various ranks using sequences of ABA triplets, where A and B differed in frequency or in F0. The participants were asked to try to hear two streams and to indicate when they heard one and when they heard two streams. F0 discrimination was measured for the same tones that were used as A tones in the streaming experiment. Both streaming and F0 discrimination worsened significantly with increasing harmonic rank. There was a significant relationship between streaming and F0 discrimination, indicating that good F0 discrimination is associated with good streaming. This supports the idea that the extent of stream segregation depends on the salience of the perceptual difference between successive sounds.

Distorting temporal fine structure by phase shifting and its effects on speech intelligibility and neural phase locking

Envelope (E) and temporal fine structure (TFS) are important features of acoustic signals and their corresponding perceptual function has been investigated with various listening tasks. To further understand the underlying neural processing of TFS, experiments in humans and animals were conducted to demonstrate the effects of modifying the TFS in natural speech sentences on both speech recognition and neural coding. The TFS of natural speech sentences was modified by distorting the phase and maintaining the magnitude. Speech intelligibility was then tested for normal-hearing listeners using the intact and reconstructed sentences presented in quiet and against background noise. Sentences with modified TFS were then used to evoke neural activity in auditory neurons of the inferior colliculus in guinea pigs. Our study demonstrated that speech intelligibility in humans relied on the periodic cues of speech TFS in both quiet and noisy listening conditions. Furthermore, recordings of neural activity from the guinea pig inferior colliculus have shown that individual auditory neurons exhibit phase locking patterns to the periodic cues of speech TFS that disappear when reconstructed sounds do not show periodic patterns anymore. Thus, the periodic cues of TFS are essential for speech intelligibility and are encoded in auditory neurons by phase locking.

Effect of Context on the Contribution of Individual Harmonics to Residue Pitch

There is evidence that the contribution of a given harmonic in a complex tone to residue pitch is influenced by the accuracy with which the frequency of that harmonic is encoded. The present study investigated whether listeners adjust the weights assigned to individual harmonics based on acquired knowledge of the reliability of the frequency estimates of those harmonics. In a two-interval forced-choice task, seven listeners indicated which of two 12-harmonic complex tones had the higher overall pitch. In context trials (60 % of all trials), the fundamental frequency (F0) was 200 Hz in one interval and 200 + ΔF0 Hz in the other. In different (blocked) conditions, either the 3rd or the 4th harmonic (plus the 7th, 9th, and 12th harmonics), were replaced by narrowband noises that were identical in the two intervals. Feedback was provided. In randomly interspersed test trials (40 % of all trials), the fundamental frequency was 200 + ΔF0/2 Hz in both intervals; in the second interval, either the third or the fourth harmonic was shifted slightly up or down in frequency with equal probability. There were no narrowband noises. Feedback was not provided. The results showed that substitution of a harmonic by noise in context trials reduced the contribution of that harmonic to pitch judgements in the test trials by a small but significant amount. This is consistent with the notion that listeners give smaller weight to a harmonic or frequency region when they have learned that this frequency region does not provide reliable information for a given task.