The Velocity of Sound in Air

“…͑9͒. For the present acoustical measurements, one of the closed ends was connected to the impedance measuring head where r wv is the fractional pressure of water vapor, in this case taken as 0.007 ͑Hardy et al., 1942;Nederveen, 1969;Kinsler et al, 1982;Caussé et al, 1984;Pierce, 1989͒. The frequency in the absence of damping then is calculated from f ϱ,th ϭc/2L, where L is the tube length specified in Table II, and given in Table III.…”

Section: Methodsmentioning

confidence: 99%

Influence of a toroidal bend on wind instrument tuning

Nederveen¹

1998

The Journal of the Acoustical Society of America

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In a toroidal bend in a cylindrical wind instrument, with the same cross section as the cylindrical part, the inertance for longitudinal waves is reduced. This induces a change in the resonance frequency. The magnitude of this change depends on the length and the sharpness of the bend and on its position in the sound field. A transition to a cylinder gives an additional inertance correction. The present study compares known results from literature and adds new facts, employing analytical and numerical methods. Possible causes of the discrepancies between measurements and theory as reported in the literature are considered. The theory was verified by measurements on some toroidal bends in between cylindrical tube pieces. Corrections were applied for diameter differences between the torus and the rest of the pipe system. Within experimental uncertainty, a satisfactory correspondence with theory was found. The results obtained in the present study determine which diameter reduction in the bend can compensate the effects of the bend on the tuning. a ratio of inner and outer radii of a bendϭ(1ϩb)/ (1Ϫb) b parameter indicating ͑local͒ bend sharpnessϭy/R 0 B bend sharpness for a toroidal bendϭr 0 /R 0 c sound speed, m/s d diameter, m f frequency, s Ϫ1 h mesh size of finite difference grid, m k wave number, m Ϫ1 K bulk modulus of air, Pa L tube length, m M inertance, kg/m 4 s p acoustic pressure, Pa Q resonator quality r radial coordinate in bore, m r 0 radius of bore, m R 0 radius of curvature of center line of a bend, m S cross-sectional area of bore, m 2 T temperature,°C u particle velocity, m/s V volume, m 3 x position coordinate, m y half-width of curved rectangular duct, m Z acoustic impedance, kg/m 4 s ␣ wall damping term ⑀ geometrically determined factor tangential coordinate in circular section angular wave number density of air, kg/m 3 Bapparent air density in bend, kg/m 3 ͑i͒ angle coordinate in bend, ͑ii͒ geometrically determined factor Φ total angle of bend length of torus measured along the center line, m phase angle angular frequencyϭ2 f , s Ϫ1 z/r 0

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“…An additional measurement channel of the meter can be used as a calibrated channel for determining the exact velocity of sound when the operating environment is unstable [19][20][21][22][23]. The transducer frequency is in 0.8… 2 MHz range.…”

Section: Overview Of Measurement Error Sourcesmentioning

confidence: 99%

Applying ultrasonic echolocation-based measurement method to increase the accuracy of leveling instruments

Petrauskas

2011

ultra

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Current mechanical, laser and electronic leveling instruments are sometimes not accurate enough to be used for determining either vertical or horizontal level for level-critical applications. By using an ultrasonic echolocation-based distance meter it is possible to design very accurate leveling instruments for a wide range of applications. This article overviews the accuracy of current leveling instruments and compares it with the achievable accuracy of the proposed leveling devices. Level determination of horizontal and vertical surfaces using mechanical devices is explained. By combining the ultrasonic distance determination method with the mechanical level determination methods, very precise leveling instruments can potentially be created. Some exemplary designs of such leveling instruments are presented. In addition, basic operating principles of an ultrasonic echolocation-based distance measurement device are presented, along with sources of measurement errors of such devices. Solutions for eliminating measurement errors are discussed. Since accuracy is the top priority, we suggest creating an isolated operating environment for acoustic measurements. A practical example of using a leveling device with implemented ultrasonic measurement method is presented along with measurement results.

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The Velocity of Sound in Air

Cited by 42 publications

References 0 publications

Atmospheric Effects on the Speed of Sound

Atmospheric Effects on the Speed of Sound

Influence of a toroidal bend on wind instrument tuning

Applying ultrasonic echolocation-based measurement method to increase the accuracy of leveling instruments

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