De Vera Institute of Technology

Old Albay District, Legazpi City, Albay

Room Acoustics

Submitted by:

Richenald C. Andamon

(_________)

BSECE-V

Submitted to:

Engr. Filomeno E. Plaza III

Professor
 Introduction

Room acoustics is the broad term that describes how sound waves interact with
a room. Each room and all the objects in it will react differently to different frequencies
of sound. Every speaker will sound different in different rooms. Acoustics are
fundamentally important to environments. The importance of acoustics is not limited to
the room. Noise can soar if they are too reverberant or too much echo, with voices
raised louder and louder to overcome the background echo.

The studio is a physical room that has an impact on the sound produced in it.
Because of this, several characteristics of sound should be considered in designing the
studio, including sound isolation, noise and vibration control, and room acoustics. When
sound strikes a surface either the studio wall or the floor, some of that sound is
reflected while some is absorbed within or transmitted through the material of the
surface. Most of the sound that hits a hard, flat surface will be reflected. However, if the
surface is irregular, it will break up the sound wave and disperse the reflections, known
as diffusion. Sound that's absorbed into the surface is dissipated within it, but
penetration occurs when sound goes through a surface and is transmitted into the space
on the other side. When a sound is produced, the direct sound is the main sound that
we hear. Nearly all spoken sound is in the range of 125 Hz (cycles per second) to 4,000
Hz, although people can hear from about 20 Hz to 20,000 Hz. All sound waves carry well
through open air, or even through small holes and cracks in walls and ceilings. Because
of the logarithmic nature of sound, a small hole will let through a lot of sound.

In a production situation, it is sound that goes from the sound source straight to
the microphone. On the other hand, indirect or reflected sound reaches the microphone
fractions of second after the direct sound does because it has traveled a circuitous
route. Reflected sound consists of echo and reverberation. Echo is the indirect sound
that has bounced off or been reflected from one surface. Similarly reverberation is the
sound after reflecting from two or more surfaces before reaching the microphone. The
components of direct and indirect sound make up what is commonly called the sound's
life cycle. In designing the audio studio, the goal is to manipulate these sound
characteristics to create a proper sound environment for production work.
Reverberation Time

It is the time required for the mean square sound pressure of a given frequency
in an enclosure, initially in the steady state, to decay after the source is stopped, to 60
dB or one-millionth of its initial value. Below is the sabine equation use for computing
the reverberation time of the studio.

V
RT 60=0.161
A
Where:

V = room volume

A = room total absorption → A=Sα

S = room total surface area

α = average room absorption coefficient

Table of absorption coefficients for a variety of surfaces

The absorption uses in the studio are concrete block, painted for the ceiling and
walls and carpet on concrete for the floor.

For Walls: Back = α bk = 0.10

Right side = α rs = 0.10 Ceiling = αc = 0.10

Left side = α ls = 0.10 Floor = α fl = 0.02

Front = α ft = 0.10
Volume of the room

V =L x W x H
3
V =6 m x 4 m x 3 m=72 m
Room surface area
2
S c =S fl =6 m x 4 m=24 m

S rs =Sls =6 m x 3 m=18 m2
2
S ft =S bk =3 m x 4 m=12m

Room total absorption

A=S c α c + S fl α fl + Srs α rs +S ls α ls + S ft α ft +S bk α bk

α
(¿ ¿ ft +α bk )
A=S c ( α c +α fl )+ S rs ( α rs +α ls ) + S ft ¿

A=24 ( 0.10+0.02 ) +18 ( 0.10+0.10 )+12 ( 0.10+0.10 )

2
A=8.88 m
Reverberation Time

V
RT 60=0.161
A
3
RT 60=0.161 (
s 72 m
m 8.88 m2
=1.31 s )
 There are two basic types of acoustic treatment - absorbers and diffusers. There
are also two types of absorbers. One type controls midrange and high frequency
reflections; the other, a bass trap, is mainly for low frequencies. All three types of
treatment are usually required before a room is suitable for making mixing decisions and
for serious listening.

Typically, the corners of the room will be prime locations where bass builds up in
the room, which is why putting bass traps in the corners is a good decision since there is
simply more bass in those locations to be absorbed, thus increasing the efficiency of
each trap. Bass will typically build up in all corners of the room. Diffusers are used to
reduce or eliminate repetitive echoes that occur in rooms having parallel walls and a flat
ceiling. Although there are different philosophies about how much natural reverberation
recording studios and listening rooms should have, all professional studio designers
agree that periodic reflections caused by parallel walls are best avoided. Therefore,
diffusion is often used in addition to absorption to tame these reflections. Such
treatment is universally accepted as better than making the room completely dead by
covering all of the walls with absorbent material. The ideal listening room has a mix of
reflective and absorptive surfaces, with no one large area all live or all dead sounding.

The four primary goals of acoustic treatment are to: to prevent standing waves
and acoustic interference from affecting the frequency response of recording studios
and listening rooms; to reduce modal ringing in small rooms and lower the reverb time
in larger studios, churches, and auditoriums; to absorb or diffuse sound in the room to
avoid ringing and flutter echoes, and improve stereo imaging; and lastly, to keep sound
from leaking into or out of a room. That is, to prevent your music from disturbing the
neighbors, and to keep the sound of passing trucks from getting into your microphones.
List of Materials or Equipments

Quantit Price Amount

Unit Description
y
125 Feet SAT-PAK COM RG 213 Coaxial Cable 15,266.08 15,266.08
LMR-400-75 type N male plugs and
2 Pcs 6,600.00 6,600.00
grounding
1 Pcs Behringer Ultramizer Audio Processor 4,400.00 4,400.00
1 Pcs Yamaha MSP3 Active 2-Way Studio Monitor 8,892.00 8,892.00
2 Pcs Techno Tamashi TH-1049 599.00 599.00
1 Pcs Alto Equalizer 31 band mono 4,500.00 4,500.00
1 Pcs Mickle MT7-USB Mixing Console 4,999.00 4,999.00
1 Set BNC Connectors and Peripherals 20,000.00 20,000.00
Broadcom FM Broadcast Antenna 87-108
1 Pcs 11,450.00 11,450.00
MHz
800 f. 10 Gauge Bare Copper Grounding
2 Pcs 8,404.00 16,808.00
Wire
1 Pcs Airman Welder 350 amp 9.9 Generator 250,000.00 250,000.00
1 Pcs Hp Envy Recline 27xt 53,679.00 53,679.00
1 Pcs Axel Oxygen 5 Broadcast Mixing Console 254,952.14 254,952.14
2 Pcs SHURE SMS57 4,356.00 4,356.00
2,118,750.
1 Pcs Armstrong FM5000B 5kW FM Transmitter 2,118,750.00
00
Mybecca Acoustic Foam Bass Trap
5 Pcs (Charcoal) Corner Wall 12" X 12" X 24" 4 3,131.00 15,655.00
Pack
3 Pcs “S2” Syline Diffuser 7,300.00 21,900
2 Pcs Acoustc Wall Panels 4 pack 7,829.50 15,659.00
TOTAL AMOUNT 2,828,465.22