By Leo L. Beranek, Tim Mellow
Acoustics: Sound Fields and Transducers is a completely up-to-date model of Leo Beranek's vintage 1954 ebook that keeps and expands at the original's unique acoustical basics whereas including useful formulation and simulation tools.
Serving either as a textual content for college students in engineering departments and as a reference for practising engineers, this publication specializes in electroacoustics, interpreting the habit of transducers as a result of electro-mechano-acoustical circuits. Assuming wisdom of electric circuit concept, it begins through guiding readers during the fundamentals of sound fields, the legislation governing sound iteration, radiation, and propagation, and basic terminology. It then strikes directly to examine:
- Microphones (electrostatic and electromagnetic), electrodynamic loudspeakers, earphones, and horns
- Loudspeaker enclosures, baffles, and waveguides
- Miniature functions (e.g., MEMS in I-Pods and cellphones)
- Sound in enclosures of all sizes, comparable to study rooms, places of work, auditoriums, and residing rooms
Numerical examples and precis charts are given during the textual content to make the fabric simply acceptable to functional layout. it's a precious source for experimenters, acoustical experts, and to people who expect being engineering designers of audio equipment.
- An replace for the electronic age of Leo Beranek's vintage 1954 ebook Acoustics
- Provides unique acoustic basics, permitting larger figuring out of complicated layout parameters, size tools, and data
- Extensive appendices conceal frequency-response shapes for loudspeakers, mathematical formulation, and conversion factors
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Additional info for Acoustics: Sound Fields and Transducers
8 also reveal that, wherever along the tube the magnitude of the velocity is zero, the magnitude of the pressure is a maximum, and vice versa. Hence, for maximum pressure, Eq. 67) applies. Specific acoustic impedance. It still remains for us to solve for the specific acoustic impedance Zs, at any plane x, in the tube. Taking the ratio of Eq. 69) to Eq. 64) or setting ZT ¼ N in Eq. 72) 44 CHAPTER 2 The wave equation and solutions p(x,t) (λ/2) t = T/4 t= n=1 3T 4 t = 0; T/2; T 0 x x=0 x=l p(x,t) 2(λ/2) 3T t= 4 n=2 t = T/4 t = 0; T/2; T 0 x=0 x x=l p(x,t) t = T/4 n=3 0 x=0 3(λ/2) 3T t= 4 t = 0; T/2; T x x=l FIG.
137) where the þ sign denotes a forward traveling wave and the À sign a reverse one. From Eq. 129) we observe that 8 pﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ > < k2 À k2 ; k ! 138) kz ¼ pﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ > : Àj kw2 À k2 ; k < kw Hence for k < kw the forward traveling term becomes an evanescent decaying one. Evanescent waves typically occur close to sound sources in the form of non-propagating standing waves. 11 SPHERICAL COORDINATES So far, we have only considered the one-dimensional spherical wave equation and its solution.
Impedance measurement. 62) which is independent of u~0 . 63) which is the principle of an impedance tube which is used for measuring samples of material for which the impedance is unknown. An elegant feature of the method is that the measurement is independent of the piston velocity or actual magnitudes of the pressures. Only the relative pressure ratio is needed to calculate the impedance. However, when the impedance is a large multiple (or small fraction) of r0c, the calibration of the microphones becomes very critical, as does the accuracy of the distances l1 and l2 between them and the sample.