# Vibrations 2 - 230515 Flashcards

Dependence of speed of sound with the temperature

Solution of the spatial wave equaion

Where does the spatial wave equations come from? Original axiom or equation?

What’s circular wave number? What do you use it for?

k = w/C

kr=1, the spherical can be regarded as a planar wave

aprox 1 meter starts the far field

Characteristic acoustic impedance? Units? Physical meaning?

pressure - voltage

particle velocity - current

characteristic acoustic impedance - resistance

Characterization sound source, which variables are independent?

sound or acoustic power (Pa), sound intensity? sound pressure, particle velocity

difference between planar and spherical waves and the properties that describe a sound source

Whats the db scale? is it a measure of what?

energy variables factor of 10, factor of 20 for?

power (whisper 0.0000..1 W, db=30), chainsaw (1 W, 120 dB)

sound intensity?

power / Area, or pressure times particle velocity, where does it come from? particle velocity and sound pressure (no phase difference)

Pl

Plane wave constant non zero sound intensity (energy is travelling), sound power is travelling

p and v

v = (1/Z0) p

p and v are in phase

Intensity depend on the other ones

Difference between spherical waves and planar waves

sound pressure amplitue changes with distance to sound source, double distance leads to a drop of 6dB

Difference between solution of spherical sound waves and planar sound waves

- complex

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Difference between ZO planar and spherical

It depends from the distance to the emitter and the wavelength

What is a freedom class u, s and p?