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Acoustic impedance tube

Test Methodfor Impedance and Absorption of Acoustical Materials by the Impedance Tube Method, ASTM C384-90a, ASTM, Philadelphia, Pa., 1990. [Pg.321]

As the design matures, the direct measurement of the acoustic properties becomes necessary. These properties include the longitudinal wave speed, the coefficient of attenuation and the acoustic impedance, which can be obtained from measurements of the reflection and transmission of sound by the material. Two acoustic techniques are available for these measurements, the impedance tube and the panel test. [Pg.248]

ASTM C 384 is another method used for acoustical materials. This method is an impedance-tube method. In the test a flexible-foam specimen is placed in a cavity over a vacuum chamber. A specified constant-air-pressure differential is then created. The air-flow value is the rate of flow of air required to maintain this pressure differential. The test is carried out 1) with air flow parallel to foam rise, and 2) with air flow perpendicular to foam rise. Air-flow values are proportional to porosity in flexible foams. [Pg.372]

With its low acoustic impedance, extreme bad width, high piezoelectric coefficient, and low density (only one-quarter the density of ceramic materials), PVDF is ideally suited as a transducer for hroad hand rmdenvater receivers in hghtweight hydrophones. The softness and flexibiHty of PVDF give it a comphance 30 times greater than ceramic. PVDF can thus he utilized in a hydrophone structure using various device configurations, such as compliant tubes, rolled cylinders, discs, and planar stacks of laminated material. [Pg.593]

In order to evaluate the acoustic properties of the various formulated composites, the sound absorption coefficients were determined by the impedance tube method according to ASTM E 1050-12. A soxmd absorption coefficients and impedance measurements instruments (Figure 16.3) made by Walen Audio Technologies, Maharashtra, India was adopted. The sample diameter was 100 mm, and each value represented the average of six samples. The soxmd absorption coefficients were measured in six frequencies 100, 200,400, 800,1600 and 3200 Hz. [Pg.375]

Fig. 7.2 Schematic of plane wave generation for acoustic measurement using 2-microphone impedance tube... Fig. 7.2 Schematic of plane wave generation for acoustic measurement using 2-microphone impedance tube...
Smaller GSA-SDS specimens (29 mm diameter) comprising 1.7 mm aerogel granules are tested for acoustic performance in the small impedance tube for frequencies from 500 to 6400 Hz. The absorption coefficients and the TL in the higher frequency range are shown in Fig. 7.10a, b. [Pg.123]

Vigran, T.E. 2012. Normal incidence sound transmission loss in impedance tube—measurement and prediction methods using perforated plates. Applied Acoustics 73(4) 454-459. [Pg.132]

Sound absorbers are usually employed for modilying the sound reverberation in a room, suppressing undesired sound reflections from remote walls (echoes), and reducing the acoustical energy density and, hence, the sound pressure level in noisy rooms. There are two standard methods of measuring absorption coefficients. One is for measuring normal incidence absorption coefficients in an impedance tube and the other is for measuring random incidence absorption coefficients in a reverberation room (Bies and Hansen, 2009). [Pg.107]

There are many acoustical methods proposed for measuring flow resistivity (Delany and Bazley, 1971 Smith and Parott, 1983). A method that uses a standard impedance tube directly to measure the static flow resistivity without any additional requirements to tube modification or sensor location change is described in ISO Standard, 10534-2 (1998) and by Tao et al. (2015). In the method, the specific acoustic impedance on the front surface of the test specimen is measured first by using the traditional transfer function method with the test specimen being placed against and with a known interval to the rigid termination, and then the characteristic impedance, the propagation constant, and the static flow resistivity are calculated based on the obtained impedance transfer functions. [Pg.111]

Fig. 5.3 shows a diagram of the impedance tube designed for the ISO 10534.2 implementation, where the test specimen thickness is 21 and the back cavity depth (the distance between the back surface of the specimen and the rigid termination) is L. The specific acoustic impedance at the front surface of the test specimen can be determined by (ISO Standard, 10534-2, 1998) ... [Pg.111]

Doutres, O., Salissou, Y., Atalla, N., Panneton, R., 2010. Evaluation of the acoustic and non-acoustic properties of sound absorbing materials nsing a three-microphone impedance tube. Appl. Acoust. 71 (6), 506-509. [Pg.127]

McGrory, M., Cirac, D.C., Gaussen, O., Cahrera, D., 2012. Sound absorption coefficient measurement Re-examining the relationship between impedance tube and reverberant room method. In Proceedings of Acoustics 2012—Fremantle, Australia. [Pg.128]

ISO 10534-2, 1998. Acoustics— Determination of sound absorption coefficient and impedance in impedance tubes— Transfer function method. International Organization for Standardization. [Pg.127]


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Impedance, acoustic

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