[Series] Lyla’s Notes on Acoustic Spaces (Vol. 3): Assembling Acoustic Space: The Choice of Anechoic Chambers, Soundproof Rooms, and Anechoic Boxes

When involved in the planning of acoustic facilities, the following assumptions are sometimes unconsciously made:

• An anechoic chamber is a fixed installation.
• Once built, its purpose will not change significantly.
• If needed, it should be built large.

However, in real-world scenarios, the measurement targets and evaluation content change at a speed that exceeds imagination:

• Transition of development phases
• Changes in product size or frequency range
• Review of required evaluation accuracy and reproducibility

Acoustic spaces, too, should be entities that are re-designed while being continuously used.

Acoustic Space is Determined by “Conditions for Establishment,” Not “Size”

In Part 2, we organized the conditions for a “measurable sound field” through the concepts of the inverse square law and environmental correction.

What becomes clear from this is that the establishment of a free sound field is not determined by:

• The size of the room itself
• The name “anechoic chamber”

What is important is to consider:

• The size of the sound source
• The target frequency range
• The distance at which reflections begin to affect the measurement

Based on these, the key is to determine how much space is necessary for the measurement to be established.

The Concept of the Anechoic Box

Organizing from this perspective naturally leads to the option of the anechoic box.

The anechoic box is often treated as a “simple anechoic chamber” or an “alternative means.” However, from a design perspective, its position is slightly different.

The anechoic box is neither:

• A smaller version of an anechoic chamber
• An advanced soundproof box

It is a design that cuts out the free sound field in the minimum unit, tailored to the measurement target.

Why the Anechoic Box is Effective

When the measurement target is relatively small and the desired frequency range for evaluation is limited:

• There is no need to prepare a large space.
• The important thing is that the measurement is completed before reflections become dominant.

In an anechoic box, by designing based on:

• The distance between the sound source and the measurement point
• The arrangement of sound-absorbing structures
• The effects of openings and boundary conditions

it is possible to secure a necessary and sufficient free sound field stably.

This is not “simple,” but rather a configuration that is neither excessive nor insufficient for the objective.

Relationship with Anechoic Chambers and Soundproof Rooms

The anechoic box is not always used in isolation.

In actual practice, it is often used in ways such as:

• Installing an anechoic box inside a soundproof room
• Cutting out a box-like section from a part of an anechoic chamber
• Integrating it into an assembly-type spatial configuration

What is important here is that anechoic chambers, soundproof rooms, and anechoic boxes are not conflicting choices.

Each possesses differences in:

• Scale
• Design flexibility
• Method of ensuring reproducibility

They are elements organized within the same design philosophy.

The Concept of “Assembling”

When we speak of “assembling” an acoustic space, it can sometimes give the impression of temporary or simple construction.

The assembly referred to here signifies design flexibility, which involves:

• Selecting the configuration according to the objective
• Cutting out the necessary performance
• Ensuring reproducibility

When viewing the finished form, an acoustic space may look like a “facility,” but its essence is the accumulation of design.

All Components Are Born from the Design Philosophy

The acoustic spaces designed by Sonola Technology are not conceived from a predetermined shape or a combination of products.

What is organized first are the design requirements, such as:

• What kind of sound field is desired to be established?
• To what extent must each element be controlled for that purpose?

According to these requirements, elements are combined to establish a single acoustic space, such as:

• Sound-absorbing structures to stably establish a free sound field
• A structural approach for simultaneously handling sound insulation, reflection, and structural vibration
• Spatial configuration methods based on the premise of reproducibility and expandability
• A design that cuts out the sound field into the smallest unit to match the measurement target

These are not individual facilities or products, but “components that constitute an acoustic space,” organized based on the same design philosophy.

What Sonola Provides is Not a “Room”

What Sonola Technology provides is not the equipment itself named anechoic chambers or soundproof rooms.

• Organizing the measurement objectives
• Determining the necessary frequency range and accuracy
• Combining sound absorption, sound insulation, and structure
• Establishing a reproducible acoustic environment

This entire series of design and construction processes is carried out consistently from the concept stage.

We Receive Consultations at These Stages

In fact, we frequently receive consultations at the following stages:

• Uncertainty about whether an anechoic chamber is necessary
• Desire to examine whether measurements can be taken in an existing soundproof room
• Desire to evaluate with a small configuration before building a large facility
• Feeling challenged by the variability of measurement results

In such cases, it is crucial not to start by assuming a facility is necessary.

Acoustic Space Planning, Starting from Design

When viewed in its finished form, an acoustic space may look like a “facility.” However, its essence is a design object.

• What do you want to measure?
• How much accuracy is required?
• Is there a possibility that the purpose will change in the future?

Assembling the acoustic space from those questions—that is Sonola’s philosophy.

When considering the new establishment, renewal, or re-examination of an acoustic space, please feel free to consult with us from the concept stage.

—— Lila Shinkai