Acoustics Advice

What is Sound	What is Frequency?	What is Hertz?	What is dB?
Sound is a vibration that typically propagates as an audible wave of pressure, through a transmission medium such as a gas, liquid or solid.  Sound is described in Frequency (Pitch) or Decibels (dB).	Frequency is the number of waves passing any point each second.	Hertz is the standard unit of measurement used to calculate the frequency of these oscillations. 1 wave per second = 1 Hertz	Decibel (dB) is a unit used to measure the intensity of a sound by comparing it with a given level on a logarithmic scale.The minimum change in volume that most humans can perceive is 3dBA.

 

How do Hertz & dB relate?

• Hertz is an absolute value, while dB will change according to environmental conditions.
• dB will be effected by the Hertz’s of multiple sources eg. Distance, temperature, white or pink noise etc

 

Question: How many Hertz in the below example?

Answer: 7 Hertz

In Building Trades, Acoustics is essentially the science of controlling sound within a building. The ABCs of acoustics cover the three main types of addressing sound:

A	B	C
ABSORB	BLOCK	COVER
Keeping sounds within the room from reverberating or echoing. NRC (Noise Reduction Coefficient) is used for rating a materials ability to absorb sound	Keeping sound within a space. STC (Sound Transmission Class) is the measurement of a material’s ability to block sound. Often referred to as Rw	Covering sound to help maintain speech privacy. White or pink noise is generally used to cover sound. White noise is man-made and is designed to provide opposite waves to the source. Pink noise is natural noise like a waterfall.

Atkar Group acoustic panels work mainly to absorb noise.

When sound is directed to a surface, some of the sound is reflected and some is absorbed in the material

Sound Absorption	Sound Transmission Loss
The ability of a material to reduce sound reflections, reverberation and echo within an enclosed space	The ability of a material to provide sound insulation or noise control from one space through to another space.
Measurement: 2 types of ratings used. NRC or Noise Reduction Coefficient (an Australasian unit of measure) or Alpha W or Aw (European)	Measurement: STC or Sound Transmission Class (older Australian way for measure). Now updated to Rw

 

Sound Absorption (NRC)

If a sound travels more than 16 metres, the human ear will pick up an echo. Hence, a room of 8 metres or more will produce an echo if the room surfaces are reflective and not absorptive.

Noise Reduction Coefficient is the average of the absorption coefficients at 250, 500, 1000, and 2000 Hz.

• It essentially measures how well something absorbs sound, mostly in the range of normal speech frequencies.
• NRC usually ranges from 0 to 1.
• A reasonable rule of thumb is that the NRC of a product is the percentage of sound a product will absorb.

Reverberation Time is the period of time it takes for sound to decay 60 decibels from its initial level. Essentially it is how long the sound will bounce around the room on reflective surfaces before it decays by 60 dB

In basic terms, If you clap your hands once, and it takes 3 second for the sound to reduce by 60 dB, then your room has an RT60 of 3.

What Reverberation Time is best for your space?

Below is an example of the general reverberation times. Please speak to your Acoustic Engineer for you advice for your project.

There is a lot of science behind this, but in simple terms, the more absorption you have in your space, the lower the reverberation.

You or your acoustic engineer will need to consider all aspects of the space to determine the reverberation rate and NRC requirements pf the spaace.

Things to consider:

• What is the core purpose of the space e.g. classroom, foyer, music theatre
• What is the size of the area – including height of the ceiling
• Are there any special considerations of the audience required e.g.. younger children, elderly, etc
• What other design aspects are being used in the space e.g.. carpet, windows, type of masonry
• Curves on walls or ceilings need special consideration as noise tends to travel back to its origin.

 

Every space has different acoustic requirements based on the level of speaking and/or learning required to ensure the space is audible and comfortable to the occupants.

Atkar Group offer many different acoustic panels with various NRC ratings. So how do you select the correct one? Below are some important things to consider:

Substrate	Finish Type	Open Area Percentage	Perforation Type
Substrate does not affect acoustic performance.	Finish type does not affect acoustic performance so you can choose from any of our Inluxe finish options.	This is the percentage of material that has been removed from the panel. The larger the percentage open area, the better the ability of the product to absorb noise but it is likely to plateau at about 30%.	If a round perforated product such as Au.diPanel has an open area of 15% and slotted product like Au.diGroove has the same open area,  you can not assume that the absorption rate is the same.

Our advice is to select the panel type you are interested in (click here to view our complete range), then get in touch with our technical support team so we can discuss your complete technical project requirements ti ensure the product is the best solution for your space.

Acousticians often recommend products that meet the required NRC ratings, but what if you want a different product to suit your design or what if your alternative product does not have acoustic data available as it is a custom product?

You just need to demonstrate through supporting reference data that it will meet the requirements.

Atkar are available to provide NRC acoustic prediction for our panels to assist with your selection – we do it almost every day!

Please contact our team to discuss your NRC acoustic requirements. You can call us on 1300 333 833 or send us a request here and we will get back to you ASAP.

Apart from the vital acoustic performance requirements outlined here, ensuring you have the correct fire requirements to meet your space is critical. Click here for advice on how to select the correct panel to meet your fire requirements.

Type: Performance Space

Architect: McIldowie Partners

Products: Au.diPanel AP250D/90 & Au.diStyle in mismatched Blackwood Inluxe Veneer and Inluxe Colour satin clear finish; Au.diSlot AS11-25/80 Blackcore MDF; Au.diSlat AX40F in Inluxe Image Spotted Gum finish.

Project: A new state of the art precinct at the University of Melbourne incorporating a 300 seat auditorium, 5 drama rooms, art gallery, music room and classrooms over 3 levels.

Requirement 1	Requirement 2	Requirement 3
Specific acoustic certification required for a performance space.	Unique 3D design but a robust finish.	Consistent sound quality in all seats

 

Solution

Area’s such as this have been specifically engineered to provide the same sound quality to seat number 3 as to seat number 103. It uses reflective panels, set at specific angles, along with absorption and diffusion panels in other areas.

A truly unique project, this exceptional design features a combination of perforated and solid triangular timber panels creating a symmetrical wave like contrast rippling in warm tones. Custom folded 3D ceiling panels wrapping down onto the walls and flowing from the entrance and into the auditorium provide optimum acoustic performance with a simultaneous visual impact. The Blackwood veneer leaves were handpicked by McIldowie Partners then applied in a mismatched style to the panels. Having established a proven track record of achievement extending over many years, McIldowie Partners had confidence Atkar would be able to deliver on expectations and collaborated closely with Atkar to develop the design.

Extensive and complicated preliminaries including 3D shop drawings and a half scale prototype were produced by Atkar assuring confidence in design before proceeding. A very impressive result, Atkar is proud to have been part of this achievement which has taken 8 years of planning, design and construction to develop this stunning multipurpose building.

Type: University Common Area

Architect: Cox Architecture

Products: 16mm Au.diGroove with American Walnut veneer and low sheen satin finish;  18mm Au.diPanel with Inluxe Veneer American Walnut and low sheen satin finish used as screen panels.

Project: A new student hub at Victoria University required an acoustic, timber veneered wall panelling with concealed fixings that could also be curved

Requirement 1	Requirement 2	Requirement 3
Curved rooms can be sensitive acoustic environments	Angle of the curve needs to be considered	Additional absorption required on the ceiling to stop noise bouncing around

Solution

Cox Architecture’s challenging list of requirements could only be satisfied with Atkar’s Au.diGroove timber veneer wall panelling as curves (particular Concave) will focus sound reflection to a single, rather noisy point.

A full scale section prototype, provided by Atkar, demonstrated the product’s ability to achieve an extreme radius of 1000mm. Cox also requested a specific American Walnut colour – selected after a thorough analysis of the comprehensive sample range provided by Atkar. Au.diPanel screens in white laminate were also installed to exacting dimensions