![]() Natural frequency of the air-filled tube. To see the effect of helium on voice quality, calculate the ratio of the nth natural frequency of the helium-filled tube to the $nth$ The quality of the voice depends on the harmonic frequencies generated by the tube larger frequencies lead to higher-pitched voices. To see why this occurs, assume for simplicity that the voice is generated by the vocal cords vibrating above a gas-filled cylindrical tube that is open only at one end. Helium, however, has the effect of giving the voice a high-pitched quality, like that of Donald Duck’s voice. This danger is for divers to breathe a mixture containing only helium and oxygen. Vorländer M, Mommertz E (2000) Definition and measurement of random-incidence scattering coefficients.Divers working in underwater chambers at great depths must deal with the danger of nitrogen narcosis (the “bends”), in which nitrogen dissolves into the blood at toxic levels. Svensson P, Fred RI, Vanderkooy J (1999) Analytic secondary source model of edge diffraction impulse responses. Suh JS, Nelson PA (1999) Measurement of transient response of rooms and comparison with geometrical acoustic models. Doctoral thesis, RWTH Aachen University, Germany Schröder D (2011) Physically based real-time auralization of interactive virtual environments. Morse PM, Ingard KU (1968) Theoretical acoustics. Find the diffraction angle theta when the frequency of the sound is (a) 5.0 kHz and (b) 5.0 x 102 Hz. The width of the doorway is 87 cm, and the speed of sound is 343 m/s. Sound emerges through a doorway, as in Figure 17.10. Medwin H (1981) Shadowing by finite noise barriers. Refraction of light at the interface between two media of different refractive indices, with n 2 > n 1.Since the velocity is lower in the second medium (v 2 < v 1), the angle of refraction 2 is less than the angle of incidence 1 that is, the ray in the higher-index medium is closer to the normal. Question: For one approach to problems such as this, see Multiple-Concept Example 3. Maekawa Z (1968) Noise reduction by screens. Kuttruff H (2007) Acoustics – an introduction. Keller JB (1962) Geometrical theory of diffraction. ![]() Spon Press, London/New YorkĬox TJ, Dalenbäck B-I, D’Antonio P, Embrechts JJ, Jeon JY, Mommertz E, Vorländer M (2006) A tutorial on scattering and diffusion coefficients for room acoustic surfaces. EURASIP J Adv Signal Process, Special Issue on Spatial Sound and Virtual Acoustics, article ID 63560Ĭox TJ, D’Antonio P (2004) Acoustic absorbers and diffusers: theory, design and application. Acta Acust Acust 91:740Ĭalamia P, Svensson, UP (2007) Fast time-domain edge-diffraction calculations for interactive acoustic simulations. J Acoust Soc Am 29:381īork I (2005a) Report on the 3rd round robin on room acoustical computer simulation, part I: measurements. J Acoust Soc Am 97:680īiot MA, Tolstoy I (1957) Formulation of wave propagation in infinite media by normal coordinates with an application to diffraction. In this chapter the fundamental effects and their quantities of sound propasgation are introduced.īass HE, Sutherland LC, Zuckerwar AJ, Blackstock DT, Hester DM (1995) Atmospheric absorption of sound: further developments. Any time a sound propagation model is discussed, it must be kept in mind its limited frequency range of validity. For audible sound these span from metres to centimetres, so there is no general solution covering all frequencies in broadband sound. Modeling of these phenomana is often a challenging task but nevertheless interesting, because many of the theoretical concepts involve approximations related to object dimensions in comparison with the acoustic wavelength. Furthermore, properties of the medium like inhomogenity of sound velocity and viscous effects can cause influences such as refraction and attenuation, respectively. In outdoor environments, sound is scattered at trees, reflected at building façades or at the ground, or it may be diffracted around a noise barrier. ![]() In indoor environments, sound is reflected and scattered at walls, floors, ceilings, and furniture. ![]() Sound waves propagate from a source into the environment where they interact with objects.
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