Acoustics and Classroom Sound Issues
-
Upload
ashvary-jain -
Category
Education
-
view
575 -
download
0
description
Transcript of Acoustics and Classroom Sound Issues
![Page 1: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/1.jpg)
AcousticsReverberation
and Classroom Issue
Ashvary Jain0201ME101017BE III sem, MechanicalJabalpur Engineering College
![Page 2: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/2.jpg)
Contents Introduction
Acoustics and Classroom
Problems in a classroom• Room Noise• Reverberation• Speaker Listener Distance
Reverberation – In Detail
Solutions
Summary
![Page 3: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/3.jpg)
Introduction
Sound
• It is a mechanical wave that undergo oscillation.
• Transmits through solid liquid or gas.
• Composed of frequencies within range of hearing or create sensation of vibration.
.
![Page 4: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/4.jpg)
Acoustics
• Study of all mechanical waves in gases, liquids, and solids.
• Including vibration, sound, ultrasound and infrasound.
• Everything related to hearing and speaking comes in its scope.
![Page 5: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/5.jpg)
What happens to sound when it hits a barrier?
• Transmitted (pass through)
• Absorbed
• Reflected
• Diffracted
![Page 6: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/6.jpg)
![Page 7: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/7.jpg)
Acoustics and Classroom
Importance of hearing/listening• Approximately 45% of school time spent listening• Approximately 30% speaking• Approximately 16% reading• Approximately 9% writing
![Page 8: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/8.jpg)
• Elements of Listening
• Detection – Identifying the sound
• Discrimination – Differentiating between various words
• Recognition – Catching the exact word
• Comprehension – Noting correct thing
![Page 9: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/9.jpg)
Problems in Classroom
Often students are not able to get what teacher is speaking, sometimes even misinterpreted. The main reasons behind this are
• Room noise
• Speaker-listener distance
• Room reverberation
Lets discuss these problems individually….
![Page 10: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/10.jpg)
Room Noise
• Acoustical noise is any unwanted sound
• Could be external or internal
• Includes whispers, shut noises, external disturbances.
• Noise is around 55-60 dB in classroom
![Page 11: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/11.jpg)
Speaker Listener Distance
• Audibility decreases as the distance from the speaker increases
• About a 6dB drop for every doubling of distance.
• At certain distance, background noise can mask speaker’s voice.
• A typical teacher’s voice measures 60 to 65dB at a distance of 1m/3ft.
![Page 12: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/12.jpg)
• Noise is generally at 55-60 dB in a classroom.
• First row student gets decent sound, about 65 dB
• Forth row student get 60 dB of voice signal, same as noise
• For back-row students, teacher is at 53dB, receive 55% of the speech signal, and achieve just 60% word recognition
![Page 13: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/13.jpg)
Reverberation
![Page 14: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/14.jpg)
Reverberation • It is the persistence of sound in a particular space after the original sound is removed.
• Large number of echoes build up and then slowly decay as the sound is absorbed
• Causes prolongation of sound.
• Longer the reverberation the more “smear” of speech sounds.
![Page 15: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/15.jpg)
Reverberation Time •Time it takes a sound to stop reflecting
•Is the time in seconds for a sound to reduce 60 dB in intensity once the generation of sound has stopped
•Hard room -> long RT time
•RT of room alters the effect of the speaker-listener distance upon sound intensity
![Page 16: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/16.jpg)
Phenomenon of Reverberation
Sound Source
![Page 17: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/17.jpg)
Classroom study of Reverberation
![Page 18: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/18.jpg)
Classroom Calculations
Time Difference Calculations
• Assuming the dimensions of a class room to be – 15 x 10x 10 metres.
• Speed of light = 330 m/s
T1 = Time taken by sound to travel via 10m straight path
T2 = Time Take by sound to travel via 12+12m reflected path
Time = Distance /Speed
![Page 19: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/19.jpg)
T1 = 10/330 = 0.0303 sec
T2 = 28/330 = 0.0727 sec
T2 – T1 = .0424 sec
10m
12m10mTime difference of .0424 sec between two sound waves cause the confusion while detecting the speech
![Page 20: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/20.jpg)
Sabine equation
Reverberation Time Calculations
RT60 - Reverberation Time in sec
V - Volume of Room in cubic metres
S - Total Surface Area in square metres
c – Speed of Light in metres
a – Average Absorption Coefficient
![Page 21: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/21.jpg)
By using a pre build Reverb Time calculator and putting data close to the reality, the reverberation time was found to be around 1.8 seconds
![Page 22: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/22.jpg)
In general, for a class room, the reverberation time must be between .4 to .6 sec
![Page 23: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/23.jpg)
Solutions for Better Acoustics
Importance of Better Acoustics
• Improvement in speech recognition• Improvement in speech recognition• Reduced vocal strain and voice fatigue for teachers• Increased teacher mobility
Some of the solutions for better Acoustics are -
![Page 24: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/24.jpg)
1. False Ceiling• Decreases the volume of room.• Time variation between two rays also reduces• Acoustical ceiling tiles in the room to decrease reverb due to
absorption• Available in panels, which are installed using a grid attached to the
existing ceiling. • Wood planks provide a similar benefit as acoustical ceiling tiles.• Thermocol sheet also help for the purpose
![Page 25: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/25.jpg)
Acoustic Tiles used as False Ceiling
![Page 26: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/26.jpg)
2. Carpeting Floor
•Helps in absorption of reverb sound.
•Replace hardwood, laminate, tile or cement floors with carpet
•cover the floors with area rugs.
•More open area on floor = more reverberation
![Page 27: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/27.jpg)
Room with good False Ceiling and Carpeting
![Page 28: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/28.jpg)
3. Heavy Fabric on Windows
•Cover windows with heavy drapes.
•Drapes made from soundproofing material are available but are costly
•Instead choose a heavy fabric that covers the entire window
•Also cover walls with heavy fabric or velvet
•Appears similar to Movie Theatre fabrication
![Page 29: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/29.jpg)
Drapes in an Auditorium
Movie Theatre Fabrication
![Page 30: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/30.jpg)
4. Mic and Speaker System
• This is specially for classrooms.
• Speakers are installed in various part of the room
• Teacher is supposed to speak on mic
•Appears as teacher being near to most of the students
•Reduces the Speaker – Listener Issue as if teacher is just near to him.
•Background noise is suppressed.
![Page 31: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/31.jpg)
An Auditorium with perfect use of Acoustic Fundamentals
![Page 32: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/32.jpg)
Summary• Acoustics make big impact on any vocal oriented operation
• Classrooms often suffer with poor acoustics
• Classroom related issues include – Room Noise, Speaker-Listener distance, Reverberation
• Various measures could be taken to enhance acoustics
• For Classrooms, this include False Ceiling, Carpeting, Drapes and Speaker-Mic system
![Page 33: Acoustics and Classroom Sound Issues](https://reader033.fdocuments.net/reader033/viewer/2022061213/5496e18eac795959288b52f8/html5/thumbnails/33.jpg)
Thank You