What Is An Anechoic Chamber? (And what it is used for)

I am still fascinated with the anechoic chamber space, having worked in speaker design for over a decade. With its foam walls and eerily silent ambience, it is a disturbingly quiet place, and, honestly, I prefer to spend time elsewhere.

An anechoic chamber is a specially designed room or space that is acoustically isolated and treated to minimise reflections of sound or electromagnetic waves. It features sound-absorbing materials on the walls, ceiling, and floor to create a nearly echo-free environment.

We use anechoic chambers for various purposes, such as audio testing, antenna measurement, and research in acoustic engineering and telecommunications.

They provide controlled conditions for accurate measurements and experiments by eliminating external noise and interference.

In the world of speaker design, they are used to test and measure new speaker designs.

In this article, I will explain what an anechoic chamber is, why speaker designers need anechoic changes and what happens to you if you spend too much time in an anechoic chamber.

What Is An Anechoic Chamber?

An anechoic chamber is an echo-free room engineered to absorb reflections of sound or electromagnetic waves completely. The term ‘anechoic’ is derived from Greek, meaning ‘no echo’. These chambers are carefully designed with special, sound-absorbing materials that line the floor, walls, and ceiling to mute echoes.

The result is a space that is disturbingly silent and ideal for precise audio testing, free from external noise and reflections.

They’re akin to entering a completely different world where the usual rules of sound do not apply, and this unique characteristic makes them invaluable in my line of work: speaker design.

What Is An Anechoic Chamber Used For?

Anechoic chambers serve multiple purposes across various fields due to their unique acoustic properties. While they might be unsettling to some, their ability to create an echo-free and noise-free environment makes them ideal for precise and controlled testing.

For example, anechoic chambers are indispensable in the realm of speaker design. They provide the perfect conditions to understand a speaker’s true character and performance, free of any external influence or reflection. This accurate representation allows for a meticulous evaluation and subsequent fine-tuning of the speaker’s design.

Furthermore, these chambers are used in the telecom industry for testing antennas and wireless devices. They allow for precise measurements without any interference from ambient signals or reflections.

Researchers also utilise anechoic chambers to study acoustics, human sound perception, and noise control techniques. The controlled environment helps them isolate variables, ensuring that their findings are as accurate as possible.

An anechoic chamber is a crucial tool in any field requiring accurate and controlled acoustic or electromagnetic measurements.

Why Are Speakers Tested In An Anechoic Chamber?

Anechoic chambers play an essential role in testing and evaluating speakers’ performance in speaker design. The distinct environment within these chambers allows designers to gauge the speaker’s sound output without any interference from external noise or reflections, offering a clear, undistorted representation of how the speaker performs.

When a speaker is tested in an ordinary room, the sound waves it emits bounce off the walls, ceiling, and floor, creating echoes that interfere with the original sound. This makes it challenging to assess the speaker’s true sound quality accurately and can lead to misjudgments in design modifications.

However, in an anechoic chamber, these reflections are entirely absorbed by the specially designed walls, floor, and ceiling, meaning the sound emitted by the speaker is the only sound we hear. This provides a ‘pure’ environment to measure the speaker’s frequency response, dispersion pattern, and total harmonic distortion without external influence.

To measure speaker sensitivity in an anechoic chamber, a measurement microphone is typically placed at a distance of 1 meter from the speaker, and the speaker sensitivity is measured on an axis powered with 1Watt. This gives an industry standard that can help consumers compare the results of speakers from different manufacturers.

By studying these unaltered results, speaker designers can identify any potential issues or areas for enhancement in their designs and make necessary adjustments to ensure the speakers provide the best possible audio experience. Therefore, anechoic chambers serve as an invaluable tool in developing and refining high-quality speakers.

What Happens To You In An Anechoic Chamber?

Experiencing time in an anechoic chamber is an interesting, if not unsettling, experience. The level of silence in these rooms is nothing like what we experience in everyday life. When you enter the chamber, you first notice the absence of sound. The silence is profound and almost tangible, giving you an immediate sense of isolation.

Some people report feeling disoriented or unbalanced in anechoic chambers. This is because, in a typical environment, our ears use the subtle echoes that bounce off walls and objects to help orient us in space. It can be disorienting when these echoes are eliminated, as they are in an anechoic chamber.

Also, without ambient noise, you become more aware of your own physiological sounds. The beating of your heart, your breath, and even the subtle rustling of your clothes become more apparent. Some people have even reported hearing their own blood circulating.

However, despite these effects, spending time in an anechoic chamber is completely safe up to a point. The disorientation or unease typically disappears once you leave the chamber and return to a more typical acoustic environment.

Can You Hear Yourself Talk in An Anechoic Chamber?

You can hear yourself talk in an anechoic chamber. However, the experience of hearing your own voice in such a space is unlike anything you might have experienced before.

In an ordinary environment, the sound of your voice reaches your ears directly and also after reflecting off walls and other surfaces, creating a natural reverb which gives depth and richness to the sound.

In an anechoic chamber, there are no reflections. Your voice doesn’t bounce back from the walls, floor or ceiling. All you hear is the sound that travels directly from your mouth to your ears, making your voice sound flat and muffled to yourself.

This can be an eerie experience, reinforcing the unsettling silence and disorientation often reported in these rooms. Despite this, being able to hear one’s own voice in an anechoic chamber further underscores the fascinating quietude of these spaces. It offers a unique perspective into the fascinating world of sound and acoustics.

How Is an Anechoic Chamber Designed?

Designing an anechoic chamber is a meticulous process that requires careful planning and precision. The goal is to create a space that effectively absorbs all incident sound or electromagnetic waves to prevent reflection.

The chamber is usually constructed as a room within a room, providing solid isolation from outside noises or signals. The interior walls, ceiling, and floor are covered with large, pyramid-shaped foam or fibreglass wedges. These wedges are designed to absorb sound or electromagnetic waves, preventing them from bouncing back into the room.

These materials are specifically chosen for their acoustic or electromagnetic properties. For sound, the wedges are typically made of foam or fibreglass. In contrast, materials like ferrite or carbon-loaded foam are used for RF anechoic chambers due to their ability to absorb electromagnetic waves.

The size of these wedges and the spacing between them depends on the lowest frequency that needs to be absorbed. As a rule of thumb, the length of the wedge should be approximately a quarter of the wavelength of the lowest frequency.

The chamber floor is usually constructed with mesh or grating, beneath which additional foam or fibreglass wedges are installed. This design allows people to walk within the room while still providing absorption of reflected waves.

Air conditioning and ventilation are also important considerations. They must be designed to minimise noise while maintaining a comfortable temperature within the chamber.

Designing an anechoic chamber demands a comprehensive understanding of acoustics or electromagnetics, materials science, and structural design. Despite the complexity of their design and construction, the result is a space that is an essential tool for many research and product development areas.

Final Thoughts

Anechoic chambers are truly remarkable spaces – a testament to the impressive feats of acoustic and electromagnetic engineering. They provide a unique, isolated environment necessary for precise and accurate measurements, playing a crucial role in product development, research, and artistic performances.

Although being inside an anechoic chamber can feel unsettling, this experience offers a rare insight into our audible perception and the intricate interplay of sound and silence. As we continue to push the boundaries of audio and electromagnetic technology, the value of these chambers will only grow, further cementing their place in the annals of scientific achievement.

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We love all things audio, from speaker design, acoustics to digital signal processing. If it makes noise, we are passionate about it.

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