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A Complete Guide to Specifying Acoustics

CategoryAcoustics
Published13 Jul 2021
Written ByRebecca Fox

There is a balance that must be achieved in creating spaces that look good but also feel good to be in and both are equally as important.

We are often absorbed by the aesthetics of a space, but what if other elements, such as noise, render a space unsuitable for the intended purpose? What if occupying the space is an unpleasant experience?

Acoustic panels are used to improve the sound in spaces through sound-wave absorption and they greatly influence the way a space feels by reducing unwanted noise and facilitating better communication.

In certain places, such as offices and learning facilities, sound management is especially important, particularly when it comes to productivity and inclusivity.

In restaurants and community spaces, acoustics assure that the patron’s experience is pleasant. This can be a critical factor in the success of the business – would you return to a restaurant if you couldn’t hear what the person next to you was saying?

How do acoustic panels work?

Sound waves can be reflected or absorbed, and the science of acoustics is largely about what to reflect, what to transmit, and what to absorb.

Sound travels until it meets resistance (for example a wall), at which point it reflects off. Acoustic panels work by absorbing this sound, subsequently making a space quieter to be in.

Acoustic panels vary in material and design and each of these elements works differently to manage the absorption (or reflection) of sound. At Decor Systems we have an extensive range of acoustic panels to suit the needs of any space both from a sound management and aesthetics point of view.

Key acoustic terminology

There are some key terms to understand when specifying acoustic panels. We go into detail about these in our CPD presentations which you can book through one of our project consultants.

We’ve pulled out the top terminology here and you can view the full acoustics glossary here.

Noise Reduction Coefficient (NRC)

Noise Reduction Coefficient is an average rating of how much sound an acoustic product can absorb.

It is a simple number index range from 0 to 100 which represents the % of sound that is not reflected off the material (in most cases the structural materials and surface finishes) and instead circulates back into the room.

A high NRC rating indicates that the material of choice is absorbing the sound which ‘deadens’ the sound in the room.

A low NRC rating indicates that the material is not absorbing sound, and is generally found in hard reflective surfaces, i.e., tiles and glass.

Decibel

Another key term that you will come across when specifying acoustics for a space is Decibel.

A decibel or dB deals with the loudness of sound. The decibel (dB) is a logarithmic unit. An increase of 3dB is twice the sound pressure or loudness.

Example: A 90dB sound event is equal to a power ratio of 1 billion. An increase of 30dB means the power ratio increases to 1 trillion!

Adding sound absorbing materials into a room will reduce the dB or the loudness of sound.

What are acoustic panels made from?

Different materials come with different acoustic ratings and are suitable for managing sound in spaces with multiple acoustic requirements. For instance, the sound will want to be managed differently in a library compared to a music room and therefore different products will need to be specified.

Most acoustic panels are made from a combination of timber with a sound-absorbing backing material.

In the Decor Systems range, you will also find acoustic products made from materials such as fibre cement, plasterboard, and mineral wool.

At Decor Systems, we try to strike a balance between acoustic panels that not only manage sound but are aesthetically pleasing. So, once you select the rating and provide our project consultants with a brief on what you’re trying to achieve, the Decor team can work with you to create a ceiling, walling or partitions that blends in with the aesthetic of the space you are designing.

When it comes to specifying acoustics, there are many factors to consider. Decor Systems should be viewed as an extension of your team so we can work together to ensure that you achieve exactly what it is you’re after.

Here are our top tips for specifying acoustics;

  • Be aware that sound, like water, will find the weakest point through. Therefore, voids in ceilings and ducts need to be addressed.
  • Understand the needs of the space. Is it going to be a space for collaboration and communication or for concentration or creativity?
  • Understand that sound travels through any medium, not just air. Structure-borne sound needs to be addressed separately from the airborne sound.
  • Good sound attenuation relies on density and airtightness.
  • Consider allowing background sound into meeting rooms to provide masking and privacy for room-to-room attenuation.
  • Sound absorption needs to be considered alongside sound insulation.
  • Employ a competent professional acoustic consultant. Your Decor Systems consultant will be delighted to assist you with this.

7 design tips for the best architectural acoustics

  • Watch out for sound reflections. Straight surfaces reflect sounds back into the central space making sound clarity muddy.
  • Select acoustical treatment carefully. Different materials absorb sound frequencies differently. Make sure your acoustical treatments are absorbing the right sound frequencies.
  • Diminish echoes when necessary. Be aware that sounds travelling within 30 milliseconds of each other are perceived without an echo. Sounds travelling after the 30-millisecond threshold become echoes of the original sound.
  • Don’t let other building systems get in the way. Noise control is important to keep in check as other building systems (like HVAC systems) operate. Keep such clashing noises to a minimum.
  • Keep objects or other obstructions out of the way. Objects that obstruct a sound path can block high-frequency sounds. (Low-frequency sounds can bend around objects.)
  • Get good pattern control. Make sure sound systems for a room get good sound coverage. This will prevent feedback and other sound distortions.
  • For out-of-the-way listening areas, get distributed sound systems. Such “delay-fill” speakers operate with an electronic delay, so the sound matches and is synchronised.

The importance of incorporating acoustic requirements in the design stage

Involving acousticians in the early stage of project design will ensure that you achieve optimal sound performance and avoid costly and unattractive band-aid solutions after project completion.

It is not always about reducing noise, but more about achieving the right acoustic outcome to make the space fit for the purpose for which it is built.

When working hand in hand with an acoustician, architects can achieve a sound acoustic outcome, overcoming many challenges that are commonly faced in the process.

The Surry Hills Community Centre, designed by Frances-Jones Morehen Thorp (FJMT), was intended to meet the various needs of the local community and includes an integrated local library, community centre and childcare centre. Each space within the centre has very different acoustic requirements which was a key challenge of the project.

Decor Systems products were specified by FJMT to assist with achieving various acoustic qualities for different users within the centre. In an article by Architecture & Design, it was addressed that in this project “the inherent high-energy and high-noise of both the childcare and community centre zones require acoustic absorption to allow users to engage and interact without excessive noise carrying into the library. To achieve this, the architects used pre-finished, fire-rated, perforated acoustic panels (DecorZen and DecorStyle – by Decor Systems) extensively throughout these spaces, achieving up to 88 per cent of incidental noise absorption.”

Your acoustic checklist

It is imperative that you plan ahead and clearly scope out your requirements in view of making the right product system specifications at the conceptual stage of your project.

Retrofitting acoustic panel systems following completion can be expensive, time-consuming, can interfere with schedules and often has a ‘Band-Aid’ look about it. Hence the need to clearly delineate and analyse potential issues beforehand in view of intelligently addressing them at the most appropriate time.

PLAN AHEAD - WHAT YOU NEED TO KNOW:

  • Room dimensions
  • Ceiling height
  • Type of lighting
  • Ventilation/Ductwork
  • Fire rating requirements
  • Environmental accreditations required
  • Potential issues
  • New Build or Retrofit?
  • Current sound treatments

DIAGNOSIS

WHAT ARE YOUR MAIN SOUND ISSUES?

PART ONE:

  • Echo
  • Excessive Noise
  • Reverberation
  • Sound Quality
  • Speech Intelligibility
  • Hearing Protection

If any of these are critical issues, you will need sound absorption products.

PART TWO:

  • Sound Transfer
  • Low Frequencies
  • Impact Noise
  • Vibration Noise

If any of these are critical issues, you will need sound isolation products.

ABSORPTION TREATMENT

It is vital that the correct level of absorption is ascertained.

  • Light Absorption
    • Typically, 5% – 25% coverage is required.
    • Typical applications include recording studios, interview rooms, conference rooms, offices, etc.
  • Moderate Absorption
    • Typically, 25% – 50% coverage is required.
    • Typical applications include theatres, open-plan offices, etc.
  • Heavy Absorption
    • Typically, 50% – 60% coverage is required
    • This is for heavy applications such as vocal booths, recording isolation booths, and other areas that require almost total absorption.

Absorption materials should be installed so that they are exposed to the source of the noise problem for it to work most effectively. In most applications, they work best if they are positioned evenly around the space you are treating.

ISOLATION TREATMENT

Some recommendations for sound isolation include:

  • Look for areas where sounds may be escaping through. Doors, windows, ductwork, vents are the common culprits.
  • Employing thicker, less compressed materials to reduce impact and/or vibrational noise.
  • Thinner, denser materials work best for sound isolation.
  • ‘Seal’ the room. Make every effort to cover every surface with an appropriate sound isolation material to prevent sound escaping or entering.

Sound isolation materials need to be installed between wall layers. For new buildings, isolation materials can be attached directly to wall studs or floor joists. For retrofit applications, isolation materials may be added to existing walls followed by additional layers of plasterboard over it; the more mass, the better the outcome!

How to stop sound from escaping

In acoustics, managing high frequencies is relatively easy compared to bass. High frequencies have less energy, and the shorter wavelengths cause the waves to be directional.

This means we can predict where high-frequency sound will travel by looking at the dispersion pattern of the PA system's horn and drawing vectors outward. By positioning acoustic panels on hard reflective surfaces, excessive echo and room ambience is attenuated.

Managing bass is an altogether different matter: bass waves are long, powerful and omnidirectional meaning that they go everywhere. This not only makes them more challenging to control inside the room but containing them is difficult, if not impossible.

When attempting to control bass from escaping, the first thing to do is to reduce the bass inside the room using bass traps. This will improve the sound of the audio system by reducing hotspots. With less energy in the room to contain, creating barriers becomes a bit easier.

The next stage is determining how the bass is escaping. Doors and windows are often a source. These are generally addressed by adding mass to or by adding a second set. In doing so, bass energy must cause the first set of doors to vibrate, which in turn must cause the second set to do the same before the sound can escape.

By introducing an air space between the two, you are decoupling the energy. Herein lays the magic to containing sound.

With walls, the trick is to build a heavy inner wall and 'float it' in front of the outer wall. This is usually done using a resilient channel whereby the inner gypsum wall is left to vibrate freely on top of the outer wall. The heavy mass requires lots of bass energy to set it in motion, introducing yet another level of thermo-dynamic energy transfer which results in less energy for the outer wall to contain.

Ceiling tiles are also a ready conduit for sound to escape. Lightweight tiles do not stop bass, it simply passes straight through which causes the floor above to vibrate. Adding a mass component such as that found in Primacoustic Thunder Tiles will help a lot.

The gypsum mass component employed in the Thunder Tiles is first set to vibrate before the sound can reach the upper floor, greatly attenuating the energy.

The air space introduced by the drop ceiling naturally decouples the two surfaces and once again, the sound is better contained.

It is important to note that bass, when driven to extremes, can cause the concrete substructure of a building to vibrate. Stopping this type of energy is practically impossible. When analysing the problem frequencies, you may find that the beams are resonating at a certain frequency and shifting the bass using an EQ can sometimes help.

Speak to the experts

Need a quick response? Our sales consultants are ready to help when you need it.

Call 1800 835 035Email letstalk@decorsystems.com.au
DECORLUX®
NRC 0.60 -> 0.75
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0.60
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0.75
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