Marshall Day Acoustics have been operating for over 40 years and have become one of the world's largest and most respected acoustic consultancies. Their team provide the highest standard of architectural and environmental acoustic consulting, which is why they were perfect for one of our recent jobs – testing the acoustic quality in the Jigsaw Office in Tauranga.
We asked Marshall Day Acoustic to recommend acoustic treatment for the lobby of the Jigsaw Architecture office in Tauranga. The installation is being used as a demonstration of dbSP Edge panels, a new product from dbsorb. We partnered with dbsorb to do a before and after comparison of reverberation time (RT) of the room.
The untreated lobby has an RT of 0.9s
Marshall Day visited the Jigsaw office on 26 April 2023 to measure the RT of the lobby in its current state. The lobby has a carpet floor and a painted concrete ceiling. The walls are a mix of concrete blockwork, timber veneer cabinets and glazing. There is an open doorway at the northern end of the room. Figure 1 below shows the layout of the lobby.
Marshall Day measured a mid-frequency RT of 0.9s for the room – an average of four different positions. The mid-frequency RT is the average of the measured RT at 500 and 1000 Hz octave bands. Although the room is called a lobby, we understand it is used for meetings as well.
Marshall Day recommends a reverberation time of < 0.6s
The Australian/New Zealand Standard AS/NZS 2107:2016 Acoustics – Recommended design sound levels and reverberation times for building interiors recommends a mid-frequency RT of < 0.6s for small meeting rooms.
We recommend aiming for a balanced RT across the frequency range. If there is too much reverberation at low frequencies compared to high frequencies the room can sound ‘boomy’ and speech intelligibility is compromised.
|
Table 1: Predicted sound absorption of dbSP Edge with and without 50mm batts Product |
Sound absorption coefficient (α) |
Noise Reduction Coefficient (NRC) |
|||||||||
|
125 |
250 |
500 |
1000 |
2000 |
4000 |
||||||
|
dbsoffit with air gap |
0.20 |
0.60 |
0.85 |
1.00 |
1.00 |
1.00 |
0.86 |
||||
|
Dbsoffit with 50mm batts |
0.35 |
0.75 |
1.00 |
1.00 |
1.00 |
1.00 |
0.94 |
||||
In terms of positioning the product, we recommend installing the dbSP Edge above the table to reduce flutter echoes between the ceiling and floor. Flutter echoes are when sound bounces back and forth between two hard surfaces, they can be distracting and reduce speech intelligibility.
Figure 4 overleaf shows our recommended location for the dbSP Edge
We have added acoustic treatment to the lobby ceiling of the Jigsaw Architecture office in Tauranga.
The lobby now has an average mid-frequency reverberation time (RT) of 0.45 seconds with a slight bass rise. This could be addressed by additional treatment with a low-frequency focus. However, feedback from Jigsaw staff is positive, and we consider that the lobby is now fit-for-purpose as a breakout/meeting room.
The treated lobby has an RT of 0.45s
Marshall Day visited the Jigsaw office on 18 April 2024 to measure the RT of the treated lobby using a mini IRIS system.
We installed 11.3m2 of 50mm dbSP Edge panels with polyester infill have been installed to the soffit, above the ornamental suspended ceiling grid.
Figure 1 below shows the RT results of the measurements before treatment, our predictions after treatment and our measurements of the treated room.
Lance Adolph Director at Jigsaw comments on the Dbsorb panels.
“My experience of the acoustics in the space prior to the DbSorb soffit panels: slightly uncomfortable in that high and low frequencies appeared noticeably louder/harsher when people were talking normally and even worse when voices were a bit elevated."
"There was perceivable reduction in the experience of the acoustics in the space following DbSorb Soffit Panel installation and particularly obvious when standing below the product. The sound experience when occupying the space below the product is now comfortable, less fatiguing."
Space outside of the product footprint remains live as there are reflective surfaces on 3 sides.
"The visual result of the installed Db soffit product met our expectations, which were high in the first instance. The folded perimeter of the panels are very tidy almost appear homogonous, without evidence of joints etc. We love the concealed fixing innovation which results in a clean, understated acoustic soffit panel. In our case the panels are black in colour, installed to underside of a black ceiling. The panels are therefore not seeking attention but performing their main, acoustic performance role."
