APPLY SOUND TRANSMISSION

TO SOUNDPROOFING

KOSHI HIGH SCHOOL 2ND GRADE TOMOHIRO IWATA YUTO OCHIAI TAKAKI SAITO KYOHEI YAMAMOTO

When our school is under construction, the noise will have a bad influence on our class. We considered how we can reduce the noise and studied how the thickness of a material affects sound transmission. In the end, we want to find the cheapest and easiest way to reduce sound transmission.

Motivation

透過音エネルギー

吸収音エネルギー （熱に変換）

Incide

nt so

und

energ

y

Reflected sound energy

Transmitted sound energy

Absorbed energy

What is sound transmission?

12mm 48mm

Use 1-6 boards 12mm or 5.5mm thick

Experiment

device Speaker

PCConstant-frequency oscillator

Experiment equipment

speaker

microphone

Front view

0 12 24 36 48 60 72

Thickness(mm)

Loud

Quiet

Transm

ission loss（

ｄＢ

）

We thought sound gets smaller and smaller by adding boards.

Expectation

　 FFT　　 (FAST FOURIER TRANSFORM)N

oise ( outside the area of m

easurement)

percentage of frequency occurring sound

percentage of frequency

frequency

-20

-40

-60

-80

-100

dB（sound

level）Experimental landscape

percentage of frequency

frequency

percentage of frequency

frequency

FFT(FAST FOURIER TRANSFORM)representing sound in terms of the frequencies of the waves that make up that signal

Experiment result

Red 　　　0mm　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　green 　　 12mm　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　blue 　　　24mm　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　yellow 　　36mm　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　light blue 48mm　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　pick 60mm　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　white 72mm

 

As the number of boards increases, we don`t see sound insulation effect.

Experiment result

0 10 20 30 40 50 60 70 800

5

10

15

20

25

Thickness (mm)

Transmission loss

(dB)

Contrary to expectations, the sound didn’t increases in proportion.

Consideration Ⅰ

0 10 20 30 40 50 60 70 800

5

10

15

20

25

Thickness (mm)

Transmission loss

(dB)

Asymptote

It seems that this graph has an asymptote.

Consideration Ⅱ

0 10 20 30 40 50 60 70 800

5

10

15

20

25

Thickness (mm)

Transmission loss

(dB)

There will never be a point where sound isn’t transmitted at all.

Consideration Ⅲ

Thickness of board(mm)

Transmission loss (dB

)

Consideration Ⅳ

transmission loss (dB

)

Thickness of board(mm)

Consideration Ⅳ

TRUSS STRUCTURE

Incident sound

Reflected sound

Transmitted

sound

OUR NEXT CHALLENGE

1. MEASURE SOUND TRANSMISSION USING A TRUSS STRUCTURE (WHICH LOOKS LIKE THE CROSS SECTION OF CARDBOARD).

2. MAKE SPACE BETWEEN THE BOARDS, 　 AND STUDY THE DIFFERENCE FROM WHEN THE BOARDS ARE ATTACHED.

3. CONFIRM THE ASYMPTOTE OF THE GRAPH.

THANK YOU FOR LISTENING ！