Inharmonicity

Abstract: A method for the estimation of the multiple pitches of concurrent musical sounds is described. Experimental data comprised sung vowels and the whole pitch range of 26 musical instruments. Multipitch estimation was performed at the level of a single time frame for random pitch and sound source combinations. Note error rates for mixtures ranging from one to six simultaneous sounds were 2.1 %, 2.4 %, 3.8 %, 8.1 %, 12 %, and 18 %, respectively. In musical interval and chord identification tasks, the algorithm outperformed the average of ten trained musicians. Particular emphasis was laid on robustness in the presence of other sounds and noise. The algorithm is based on an iterative estimation and separation procedure and is able to resolve at least a couple of most prominent pitches even in ten sound polyphonies. Sounds that exhibit inharmonicities can be handled without problems, and the inharmonicity factor and spectral envelope of each sound is estimated along with the pitch. Examples are given of musical signal manipulations that become possible with the proposed method.

Abstract: Pitch conveys critical information in speech, music, and other natural sounds, and is conventionally defined as the perceptual correlate of a sound's fundamental frequency (F0). Although pitch is widely assumed to be subserved by a single F0 estimation process, real-world pitch tasks vary enormously, raising the possibility of underlying mechanistic diversity. To probe pitch mechanisms we conducted a battery of pitch-related music and speech tasks using conventional harmonic sounds and inharmonic sounds whose frequencies lack a common F0. Some pitch-related abilities - those relying on musical interval or voice recognition - were strongly impaired by inharmonicity, suggesting a reliance on F0. However, other tasks, including those dependent on pitch contours in speech and music, were unaffected by inharmonicity, suggesting a mechanism that tracks the frequency spectrum rather than the F0. The results suggest that pitch perception is mediated by several different mechanisms, only some of which conform to traditional notions of pitch.

Abstract: Two experiments are described in which the effects of acoustic parameters, and changes in those acoustic parameters, on the salience of 42 pre-selected adjectives are explored. In experiment 1 four sets of seven stimuli each varying only along one of the four acoustic parameters pitch, speed, inharmonicity and rhythm were scaled along the 42 adjectives. Parameter-adjective associations showing significant effects both in terms of consistency (Kendall's W') and in linear mapping (regression) numbered 7 for pitch, 3 for speed, 2 for inharmonicity and 1 for rhythm. Three of the four parameters produced significant levels of both consistency and linear mapping for the adjective 'urgent'. In the second experiment, the overall meaning of complete within-parameter stimulus sets were explored and many differences both within and between parameters and adjectives were found. The results were used to design five trend monitoring sounds for helicopter flight, three of which are described in detail in this paper.