Intensity of a Loudspeaker, What's wrong with calculation?

Click For Summary
SUMMARY

The discussion focuses on calculating the intensity, displacement amplitude, and pressure amplitude of a loudspeaker system emitting sound isotropically at a frequency of 1770 Hz and an intensity of 0.892 mW/m² at a distance of 5.66 m. The relevant equation used for displacement amplitude is sm = (2I/ρvω²)¹/², where ω is calculated as 11121.24 Hz. The user encountered difficulties in obtaining the correct displacement amplitude, which was calculated as 5.895 x 10-6 m, and expressed confusion regarding the relationship between intensity and amplitude.

PREREQUISITES
  • Understanding of sound intensity and its relation to distance
  • Familiarity with the wave equation for sound
  • Knowledge of basic physics concepts such as frequency and amplitude
  • Proficiency in algebra for manipulating equations
NEXT STEPS
  • Study the derivation and application of the wave equation for sound
  • Learn about the relationship between intensity and amplitude in sound waves
  • Explore the concept of spherical wave propagation and its impact on intensity calculations
  • Investigate the calculation of pressure amplitude from displacement amplitude in acoustics
USEFUL FOR

Students studying acoustics, physics enthusiasts, and anyone involved in sound engineering or loudspeaker design will benefit from this discussion.

Malavin
Messages
4
Reaction score
0

Homework Statement


A certain loudspeaker system emits sound isotropically with a frequency of 1770 Hz and an intensity of 0.892 mW/m2 at a distance of 5.66 m. Assume that there are no reflections. (a) What is the intensity (in mW/m2) at 30.8 m? At 5.66 m, what are (b) the displacement amplitude and (c) the pressure amplitude of the sound? Take the speed of sound to be 343 m/s and the density of air to be 1.21 kg/m3.

I mostly need help with part b, I believe I can get part c with the answer from part b.

Homework Equations



I = 1/2(ρvω2sm2)

The Attempt at a Solution



So, for part b and from the relevant equation:

sm = (2I/ρvω2)1/2

ω = 2πf = 2*3.14159*1770 = 11121.24 Hz

So, using the above equation and plugging in I = 0.892 mW/m2, ρ = 1.21 kg/m2, and v = 343 m/s, I get the answer 5.895 x 10-6 m. However, this answer is apparently wrong, and I'm not sure why. Is there something wrong with my calculations?
 
Last edited:
Physics news on Phys.org
intensity is the power/area covered. Such areas are usually spherical. so at a distance of 5.66meters,

.892E6W=
8.92E5W/m^2=power(dE/dt)/4pie(5.66)^2 if this really is a sphere and get power using algebra.

once you get power, intesity=power/4pie(30.8)^2 I don't get neither b or c. lol I didnt study pressure yet. I don't even know what amplitude affects.
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
11
Views
3K
  • · Replies 9 ·
Replies
9
Views
3K
Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
Replies
6
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K