Acoustics

Music associated with the Creole people, of mixed European and African descent, in the gulf region of the United States, particularly Louisiana. For further discussion see articles on Jazz, New orleans, New Orleans music, Swamp Pop, and Zydeco. louis moreau Gottschalk integrated Creole folk music into his compositions. Well-known Creole musicians include ...

The repetition of sound after a short time interval. In addition to the applications discussed below the term is used for a signal-processing device (also known as a delay) that produces a slightly delayed playback of sounds either by a tape loop or by digital delay; see Electric guitar §2 .

See also Organ stop .

Natural echoes arise from the reflection of a sound wave by a solid surface, such as a wall or cliff. For the echo to be perceived as distinct from the original sound, the extra path length travelled by the reflected sound wave must have a minimum value of around 17 metres, corresponding to a minimum time interval of 50 milliseconds between direct and reflected sounds.

The reverberant sound field in a concert hall is created by multiple reflections of sound waves. In a well-designed hall, the direct sound reaching a member of the audience is followed by a series of reflections within a time interval of around 35 milliseconds. These ‘early delayed arrivals’ are not heard as separate echoes; because of the ‘precedence effect’ they are perceived as a reinforcement of the direct sound. Subsequent reflections blend smoothly into the reverberation. A concave surface, focussing sound waves into a particular part of the hall, can give rise to an audible echo; a ‘flutter echo’ can arise from successive reflections between parallel walls....

Many types of instruments throughout the world have been assigned male, female, or sometimes ambivalent gender. These attributes, rooted in prehistoric animism and sexual dualism, bear on the perceived nature of the instruments themselves (which might be thought to embody male or female spirits, or to personify abstract sexualities) and also on their musical and social functions and the circumstances surrounding their making and playing. Even if an instrument is not given a gender, customs may govern whether it is appropriate for use by men or women or both. An attribution depends on many aspects of an instrument and a society’s attitude toward those aspects, among them morphology (e.g. phallic, like many bagpipes; womblike, like many bells and drums; or evoking pregnancy, like the rounded body of a lute), material, means of sound production (e.g. blowing, beating, stroking), high or low pitch, sound quality and power or affect, degree of apparent physical effort involved in playing, and playing posture (e.g. many Victorians considered holding the cello between the legs unladylike; in Kerala, India, a woman who raises her hand near her breast in order to strike a drum could appear immodest)....

Form factors for loudspeakers designed for proximity to the ear. Ear buds and in-ear headphones are inserted into the ear canal, circum-aural headphones fit over the entire outer ear, and supra-aural headphones are placed against the outer ear. The addition of a microphone near the mouth produces a headset useful for two-way communication.

Two important implications of the closeness of the loudspeaker drivers to the ears are binaural listening and electro-acoustic efficiency. Binaural listening, in which each ear receives a dedicated signal without inter-aural crosstalk and devoid of the acoustic signature of the actual listening space, is essential to some forms of audio research and opens the door to the creation of new perceived environments through a range of signal processing techniques focused on the localization and spatialization of sound. Headphones need only a small fraction of the sound power required by traditional loudspeaker enclosures placed at a distance, and this efficiency is crucial for the portability of battery-powered devices....

Jazz manouche, also known as ‘Gypsy jazz’, is a musical style based primarily on the 1930s recordings of French jazz guitarist Django Reinhardt (1910–53) with the Quintet of the Hot Club of France. Well-known 21st-century exponents include Biréli Lagrène, Stochelo Rosenberg, Angelo Debarre, Tchavolo Schmitt, and Adrien Moignard. The style characteristically features stringed instruments (primarily the acoustic steel-stringed guitar, violin, and double bass) in ensembles of between three and six musicians. Repertoire largely comprises American and French popular songs dating from the 1920s and 30s, such as ‘All of Me’, and tunes composed by Reinhardt, such as ‘Minor Swing’, ‘Nuages’, and ‘Django’s Tiger’. Performances consist of accompanying guitarists playing a duple-meter percussive chordal stroke called la pompe over a pizzicato walking bass line while soloists take turns improvising virtuosically on the harmonies of a cyclically repeating form, typically 32 bars long (see example). Improvised melodies often use techniques derived from Reinhardt’s recordings; eighth notes are swung and tempi vary considerably, sometimes exceeding 300 quarter notes per minute. Jazz manouche originated in the late 1960s, when music inspired by Django Reinhardt’s improvisations and repertoire began to be played in some Romani communities (the term ‘jazz manouche’ was never used during Reinhardt’s lifetime and did not gain currency until around the year ...

A transducer that converts a signal from the electrical domain into the acoustical, transforming a pattern of changing electrical voltages into a similar pattern of changing air pressures.

Whenever electricity flows, it is accompanied by a magnetic field. Play an audio signal through a wire, and a changing magnetic field forms around it, a magnetic analogy for the electrical variations within. Let that wire’s changing magnetism interact with a fixed magnetic field and it will be pushed and pulled back and forth, a mechanical realization of the electrical signal. When that conductor has a flat ribbon shape, it can energize the air directly and is the basis for a ribbon loudspeaker. Make the conductor a coil of wire and attach it to a piston light enough to vibrate quickly, yet rigid enough to move the air around it, and a moving coil loudspeaker is born.

The loudspeaker driver is often enclosed in a box, with the practical benefit of protecting the components and the acoustical effect of influencing its spectral resonance. Multiple loudspeakers, each optimized for performance in a specific frequency range, may be assembled into a single loudspeaker system whose total output is the sum of the behaviors of the individual speakers—woofers for low frequencies, tweeters for high frequencies, and midrange drivers in between. Subwoofers are systems designed specifically for the lowest frequencies. The electronic crossover circuitry spectrally divides the signal among the specific drivers in a multi-way loudspeaker system. Horns may be fitted on a driver for more efficient and more directional sound radiation. Very small loudspeakers placed over the ear or in the ear canal make-up headphones and ear buds. The loudspeaker is an essential element of some of the most important musical instruments in contemporary popular music styles: DJ mixers, synthesizers, and electric guitars. In addition to material science and manufacturing innovations, loudspeaker development relies increasingly on digital signal processing for detailed measurements, high quality filtering, and room correction....

This article is concerned with the history of vibration theory as it relates to music. For further information see Acoustics and Sound.

Sigalia Dostrovsky, revised by Murray Campbell

The basic ideas of the physics of music were first obtained in the 17th century. Acoustic science then consisted mainly in the study of musical sounds; in fact, music provided both questions and techniques for the study of vibration. Music gave experience in comparing the pitch and timbre of tones, and so the means for careful experiment on sound; musical instruments offered empirical information on the nature of vibration; and, rather remarkably, the Pythagorean ratios of traditional music theory provided frequency ratios.

Early in the 17th century it was realized that the sensation of pitch is appropriately quantified by vibrational frequency – that is, pitch ‘corresponds’ to frequency. This realization came as part of a preliminary understanding of consonance and dissonance. Once the correspondence had been made, it was possible to determine the relative vibrational frequencies of tones from the musical intervals they produced. When relative frequencies were known, there was the challenge of determining frequencies absolutely; and the first measurements were made during the century. The idea that pitch corresponds to frequency motivated efforts to understand overtones, since, during most of the 17th century, it seemed paradoxical that a single object could vibrate simultaneously at different frequencies. This paradox was resolved by the end of the century through an initial understanding of the ‘principle of superposition’. Also by this time the connection between overtones and timbre was noticed, and beats were explained quantitatively. During most of the century, sound was described as a succession of pulses, its wave nature being understood qualitatively. But late in the century the first mathematical analysis of the propagation of sound waves was made....