# ps05 - ASSIGNMENT 5 Physics 218 Due Friday October 1 Fall...

This preview shows pages 1–2. Sign up to view the full content.

ASSIGNMENT 5 Physics 218 Due Friday October 1 Fall 2004 1. A singer in the Metropolitan Opera needs to hold a certain note at a sound level of 80 dB (dynamical level approximately ff or fortissimo) for 1 s. Acoustics of concert halls is very complicated and the reﬂections from all surfaces in the auditorium (including the members of the audience) are very important elements in determining what is heard. However, we can get some idea of the sound energy produced by the singer if we ignore these complications and calculate intensities in two extreme approximations – the sound wave has uniform intensity in the whole volume of the opera house, or the sound intensity varies as 1 /r 2 where r is the distance from the singer (as in a spherical wave). The Metropolitan Opera house is very roughly a cube with lengths of the sides d = 30 m. (The actual volume is about 25,000 m 3 instead of 27,000 m 3 .) We can think of the stage as centered in one side of the cube at the level of the bottom surface of the cube. (a) Assume that the sound intensity is uniform at a level I = 80 dB throughout the volume. Then calculate the power P u passing through an area S = d 2 and the energy E u that passes through the area in t = 1 s. (b) Now assume that the singer radiates the sound uniformly in 1 4 of the volume (or area) of the sphere and that the sound is perfectly absorbed when it hits any surface. Then

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern