1 / 16

Acoustics and Concert Halls

Acoustics and Concert Halls. Stephanie Hsu March 21, 2005. Difficulties of Acoustic Design. Purpose of hall Expense in achieving ideal acoustics Drawings actual hall. Sound Waves. waves: means of transmitting energy from point to point.

chika
Download Presentation

Acoustics and Concert Halls

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Acoustics and Concert Halls Stephanie Hsu March 21, 2005

  2. Difficulties of Acoustic Design • Purpose of hall • Expense in achieving ideal acoustics • Drawingsactual hall

  3. Sound Waves • waves: means of transmitting energy from point to point

  4. Ground provides base for energy to be directly received or transmitted • Flat and hard surfaces

  5. If “perfectly reflecting,” sound will simply keep bouncing back and forth • Perfect reflectors = “Eternal sound” • Low absorption

  6. Loudness vs. Intelligibility • Surfaces around communicator increases efficiency of energy transfer • Goal of acoustic design: achieve balance between • Need to deliver sufficient energy from sourcelistener • Need for good intelligibility

  7. Loudness vs. Intelligibility (cont’d) • Bathrooms • Low absorptioneasy production of high level of sound • Multiple reflections (i.e. reverberation): sufficient overlap of successive sounds blurs out “defects” in sound

  8. W. B. Sabine • Harvard lecture room—too reverberant • Calibrate absorption of cushions, curtains, people, etc. • Measured length of cushion/amount of absorption needed to bring time of reverberation back to original value

  9. Amount of absorption present X Time of reverberation = Constant • Open window: most perfect absorber • o.w.u.s still used as measures of absorption

  10. Desirable Reverberation Rates • Time of reverberation: time taken for energy density of a sound to fall to the level of the threshold of hearing from a given level of sound • (a + x)T = kV • a=amount of absorption in empty room • x=amount of sound added • T=time of reverberation • V=volume of room • k=0.171 (works for rooms of many different shapes and sizes)

  11. Absorbents & Reflectors • ½ dead ½ reverberant room • Absorbent on back wall needed to prevent echoes or “flutter effect”

  12. Methods of Acoustical Design • Small scale model of hall • 1/8 actual size • Recording test sounds (dead enclosure) • Played at 8X normal speed inside model • Resulting sound recorded • Played back at 1/8 speed • Polystyrene foam blocks

  13. Adjustment of Acoustics • Changes in distribution of absorbing and reflecting surfaces • Movable parts of walls or reflectors can be changed to suit different purposes • Electronic modification of acoustic characteristics • Microphones in front, loudspeakers in sides and back • Microphones in space between suspended and structural ceiling

More Related