Class Notes (806,430)
Psychology (4,968)
PSYCH 3A03 (56)
Paul Faure (56)
Lecture

# Simple versus Complex Sounds.docx

3 Pages
61 Views

School
McMaster University
Department
Psychology
Course
PSYCH 3A03
Professor
Paul Faure
Semester
Fall

Description
September 20 , 2013 Psych 3A03: Acoustics Simple versus Complex Sounds Sound Attenuation by Radiation - A point source transmits sound energy as an ever expanding spherical wave front - Acoustic power is radiated equally in all directions - As sound sphere expands, the total energy emitted from the source becomes distributed over an exponentially increasing spherical surface area (SA) 2  Surface area of sphere = 4πr - Distance from the sound source can aid us to measure the amplitude to measure the surface area of a sphere - The total power (watt) of the source equals the intensity times the sphere’s surgace area (I x SA)  Power = I4πr 2 Spherical Spreading - Inverse square law. The amount of energy per square meter on a sphere’s 2 surface decreases by 1/r (r = radius of sphere) - Energy at twice the distance from the source is spread four times the area and thus has one-quarter the intensity - Intensity at surface of sphere: Inverse Square Law and Decibels - At 2x distance from source (2r), intensity is ¼ that at source distance (r). Intensity is related to power by:  , (W = power in watt) - Intensity is related to pressure: Intensity proportional to pressure 2 - At 2r pressure will be √(¼) or ½ that of the source  dB = 20log [10/P x ref  dB = 20log [102]  dB = -6.02  At twice the distance the pressure will be 6dB less - Sound pressure level decreases by 6dB for each doubling of distance (dd) from a spherical point source Spherical Spreading: Inverse Sauqre Law - Loss in energy follows inverse square law - Relative sound intensity is proportional to the reciprocal of relative change in distance squared  , where  d x new distance  d = reference distance ref  Can now calculate for any changing relationship Inver Square Law and Decibels - Relative sound intensity is proportional to the reciprocal of relative change in distance squared I 1/[d xd ]refwhere: d = xew distance and d ref= reference distance - dB equation for intensity is: 2  dB = 10log 10/(d
More Less

Related notes for PSYCH 3A03

OR

Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Join to view

OR

By registering, I agree to the Terms and Privacy Policies
Just a few more details

So we can recommend you notes for your school.