Vibrations 2 - 230515

Question 1

Dependence of speed of sound with the temperature

Question 2

Solution of the spatial wave equaion

Question 3

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

Question 4

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

Answer 4

k = w/C
kr=1, the spherical can be regarded as a planar wave
aprox 1 meter starts the far field

Question 5

Characteristic acoustic impedance? Units? Physical meaning?

Answer 5

pressure - voltage
particle velocity - current
characteristic acoustic impedance - resistance

Question 6

Characterization sound source, which variables are independent?

Answer 6

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

Question 7

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

Answer 7

energy variables factor of 10, factor of 20 for?
power (whisper 0.0000..1 W, db=30), chainsaw (1 W, 120 dB)

Question 8

sound intensity?

Answer 8

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

Question 9

Pl

Answer 9

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

Question 10

p and v

Answer 10

v = (1/Z0) p
p and v are in phase
Intensity depend on the other ones

Question 11

Difference between spherical waves and planar waves

Answer 11

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

Question 12

Difference between solution of spherical sound waves and planar sound waves

Answer 12

• complex
  *

Question 13

Difference between ZO planar and spherical

Answer 13

It depends from the distance to the emitter and the wavelength

Question 14

What is a freedom class u, s and p?