What if you are put in your closed room with no light. You then start hearing the beating of your heart so loud, flowing blood in your veins, lungs gasping for air, etc Then, you are in an anechoic chamber and it’s the quietest room in the world.
In 2018, Orfield Laboratories in Minnesota built the quietest room in the world with background noise of -9.4 decibels (dB). But as of now Microsoft Anechoic chamber at Microsoft’s headquarters in Redmond, Washington, is the quietest chamber in the world with background noise of -20.6 decibels (dB).
In this post we are going discuss what makes anechoic chambers the quietest room in the world. Moreover, we will discuss the uses and why build a anechoic chamber.
Sound
In simple terms, sound is the reception of vibration produced by an object by our ear and perceived by our brain. Sound needs a medium to travel like gas, liquid and solid.
Speed of Sound
Speed of Sound is the distance it travels in 1 second. The speed of sound is different in different medium and varies with temperature. Generally, speed of sound is 343 meters per second(m/s).
Speed of Sound in Different Medium
| Medium(680 F) | Speed Sound (m/s) |
| Air | 343 |
| Water | 1437 |
| Wood | 3850 |
| Glass | 4540 |
| Aluminium | 6320 |
Measurement of Sound
Decibels(dB) is the quantity to measure sound. It is actually the measurement in sound pressure in any medium. The frequency ( number of times particles vibrates by sound in 1 second) of sound is measure in Hertz (Hz).
1000 Hz= 1 kilo Hertz (kHz)
Types of Sound
Based, on frequency sound and our hearing perception is into 3 types. To list they are
1. Audible Sound
These is the type that is audible to human ear comfortably. The frequency of audible sound ranges from 20 Hz to 20 kHz. Tuning fork, human vocal cords, etc produces this type of sound
2. Infrasonic SOund
The frequency of infrasonic sound ranges is less than 20Hz. Earthqukes, volcanic eruption, ocean waves, etc produces this type of sound.
3.Ultrasonic Sound
Sound having frequency more than 20kHz, falls in this category. Human cannot hear this type of sound. But, certain animals like dog, bat, mosquito can detect this type of sound.
An interesting fact, human baby up to 5 years can hear this type of sound.
Decibles (dB)
We have already known, Decibels (dB) is the unit to measure sound. Higher the decibel, louder the noise and vice versa. For example, whispering produces is 30dB, Lawnmower produces 90 dB and Fireworks produces 145 dB. Decibel Meter is the instrument to measure sound.
Safe Sound and Unsafe Sound
Sound having more decibels is unsafe for our health and main cause of sound pollution. Sound at or below 70 dB is generally considered safe sound. Any sound at of above 85 dB is unsafe sound. It is more prone to cause damage to your hearing over a certain period of time.
Examples of Sound Around You
Rustling Leaves (20 dB)
Rustling of Leaves produces 20 dB. This decibel level is considered relaxing to human ear. It is the stock sound used in any mediation apps.
Refrigerator Sound (40 dB)
Most of the household appliances available in our home produces 40 dB. It is safe for our ears.
Elephant Trumpeting (112 dB)
The trumpeting sound of elephant has a decibel level of 122 dB. From a distance of 1.5 kilometers away, other elephants can hear this sound.
Jet Plane(150 dB)
The takeoff of jet plane engines produces a decibel level of 150 dB. We can hear this sound from a distance of 25 kilometers away,
NASA Saturn V (220 dB)
Nasa’s rocket Saturn V is a rocket made for moon exploration. It’s take off produces a decibel level of 220 dB. This much decibel level can melt concrete.
Anechoic chambers
Anechoic chambers are room that are made to completely absorb sound. It is like vacuum but sound vacuum. Sound absorbing materials is used to make this type of rooms. It is applied to walls, ceiling and floor.
Materials to make Anechoic chambers
The materials used to make quietest room in the world absorbs radio waves and microwave energies. Let us see the different materials used
- Closed Cell Polyurethane/ Polystyrene Foam
- Ferrite Tiles
- Mixed Cell Linings
- Fire Resistant Paint
Closed Cell Polyurethane/ Polystyrene Foam is urethane foam loaded with carbon and cut into long pyramidal shape.It is alos painted with fireproff aint.
Uses of Anechoic Chambers
#1. To test radiated emission and radiated immunity for new product.
#2. Measurement of electromagnetic field of an equipment
#3. Product compliance with emission and immunity standards.
#4. Used in Aerospace, Automotive, Medical, etc industries.
#5. Measuring of Radio Frequency properties of antennas and tags.
Microsoft Anechoic Chamber- the quietest room in the world
The quietest sound in earth is Brownian motion of particles in a gas or liquid. Next to it is vacuum that is absence of sound. It is to note that the human threshold is for hearing sound is 0 dB.
This room’s floor has the lowest sound ever recorded at -20.6 dB. So, it is considered as the the quietest room in the world.
This quietest room in the world has used the following equipment’s for testing the sound.
Surface Speakers
Customized speakers were made that characterizes the acoustic properties of the speakers. They have built customized speakers from component level to the integrated systems.
Surface Microphone
This type of microphone were used to evaluate the following things.
- Dynamic Range
- Frequency Response
- Total Harmonic Distortion
- Acoustic Seal
Cortana
Real world scenarios sound was created by Microsoft Crotona. Stress was put on speech recognition. So, to better understand its performance.
The Quietest Room of the World
Microsoft’s quietist room of the world in situated in Building 87 of its headquarters in Washigton. This building has 3 anechoic sound chambers.
The largest anechoic chamber has its own foundation. It is separated from rest of the room of Bulidng 87. The entire room sit on top of springs. There are in total 68 damping springs on top of cement foundation.
The walls, floors and ceiling of this quietest room of the world are covered with protruding foam.
Use of Microsoft’s Quietest Room of the World
Electronic devices like microphones, headphones and speakers is tested in this chamber. Moreover, Microsoft’s Surface Tablets, Xbox and Holo Lens was been tested here.
Conclusion
So, we have how Microsoft Anechoic chamber has entered the Guinness Book of Record for being the quietest room of the world. We also gave some basic knowledge of sound, its types, how it is measured.