PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Prediction methods and evaluation of high sound insulations (I)Ir. Maarten LUYKX MSc 1;
1

Peutz Consultants BV, Netherlands, www.peutz.eu

ABSTRACT
When consulting pop venues or cinema's with critical spaces like dwellings nearby, high sound insulations
will have to be realized. In an early stage of the design the related structural consequences will have to beknown very stringently and reliable, because adaptations afterwards are usually not possible. In a recentsituation with dwellings lying diagonal directly above a pop venue a high sound reduction for the roof ofthe pop venue of RA,house≥75 dB had to be realized to limit exterior noise transmission towards the facade ofthe dwellings. The interior noise transmission towards the dwellings had to full fill at least D nT,A,house≥90 dB.
Question was what structural principles would be necessary to reach these values? Based on a practicalprediction method for the sound insulation value in the key octave band (63 Hz) for a heavy double roofstructure, a heavy separated double concrete roof (f 0<3 Hz) was designed and implemented, combined withfully vibration isolated bearings (<10 Hz) under the pop hall as well as under the dwellings. The latterdemanded specific high pressure vibration insulated mountings to be designed and implemented. In order toevaluate the prediction method used for the double roof and to see whether the high sound insulations thatwere predicted have actually been realized, measurements after delivery have been performed, using a
special measurement setup with 18 subwoofers producing noise levels of 125 dB(A) house spectrum inside
the pop venue. Measured values of R A,house=76-79 dB and DnT,A,house=99 dB show that the prediction method
used proved its value and that the goals set have been met, whereas further investigation is recommended
for subsequently fine tuning the prediction model for instance for the influence (absence or presence) ofmineral wool as damping material in the void between the double concrete roof.
Keywords: Sound, Insulation, Transmission

1. INTRODUCTION
The brief for the new popvenue Doornroosje in Nijmegen for the contractor Klokbouw-Zublin
was to combine three buildings on a small footprint: a pop centre with two pop halls (1100 and 400seats) and a cafe, a bicycle parking (4000 bicycles) and hundred 4-room dwellings for students.
According to the brief both pop halls should be suitable for pop concerts with an equivalent soundlevel of 105 dB(A) house spectrum at the mixing desk and the cafe should be suitable for 100 dB(A)popspectrum.
The maximum allowable music levels in surrounding spaces were set as 40 dB(A) in the foyers
and 30 dB(A) in the adjacent pop hall. Legal limits were a maximum equivalent music level ofLAeq =30 dB(A) on the façade of dwellings and L Aeq =15 dB(A) inside the dwellings. Based on thesedemands the following sound insulations should be met:
 R’ A,house ≥75 dB for the roof of the pop hall; D’ n,T,A,house ≥90 dB between pop hall and dwellings.
 D’ n,T,A,house ≥65 dB between pop hall and foyers; D’ n,T,A,house ≥75 dB between pop halls;

1 m.luykx@peutz.nl

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2. DESIGN ASPECTS OF THE SOUND INSULATION
2.1 Prediction of the sound reduction of the roof
The demands for pop concerts have primarily determined the design of the sound insulation.
Based on earlier experience with a double concrete roof (f 0 <5 Hz) where a practical sound reductionof R’ A,house ≥70 dB was required, a similar practical prediction method was used for the design for theunderlying roof of the pop venue that should full fill R’ A,house ≥75 dB. Based on this value a
corresponding sound reduction value R' for the predominant 63 Hz octave band of at least R(63Hz)=62 dB was determined.
As a practical prediction method an estimation of the sound insulation of large, heavy double
structures for the predominant 63 Hz octave band is made based on extrapolation from the resonancefrequency with an increase of 14 to 15 dB for each octave up to the 63 Hz octave band, assuming azero insulation at the resonance frequency itself. Above the 63 Hz octave band the estimatedincrease of the sound insulation is limited to 9 dB/octave up to the 500 Hz band, and above the 500
Hz octave band the predicted increase is limited to 5 dB/octave.
Based on these assumptions a maximum value for the resonance frequency of f 0 =3 Hz could be
deduced for the double concrete roof. Based on this value for the resonance frequency the roof build
for the large pop hall was designed as follows from inside to outside: an interior roof/ceiling of 900 – 1000 kg/m2 concrete, forming the inner roof of the concrete
box of the pop hall that should be completely separated from the outer roof structure; an air void of at least 1,3 – 1,5 m with a layer of mineral wool (if necessary), with sufficientheight for the bearing structure of the large span of the outer roof. For the small hall, due to
its lower height, a higher void (>3,5 m) resulted between the inner and outer roof, which
was used for technical space.
 an exterior roof of at least 500 kg/m2 concrete.
The estimated octave band spectra for the sound reduction values R' for the roof of the large pop
hall is given as a red line in figure 1, resulting in an estimated prediction value of R’ A,house =75-78 dBfor the large hall. The measured values indicated in the graph will be treated later.

Figure 1 – Sound reduction R' of roof of the large pophall.
The estimated octave band spectra for the sound reduction values R' for the roof of the small pop
hall is given as a red line in figure 2, resulting in an estimated prediction value of R’ A,house =82-85 dB
for the small hall.

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Figure 2 – Sound reduction R' of roof of the small pophall
2.2

Final build up of the roof of the pop halls

The final build up of the double roof of the large pop hall can be clearly seen in figure 3, in
which the final height of the air void of 1,25 m is indicated as well as the complete structural
separation (dilatation) between both roofs which is necessary to reach the required direct soundreduction of R’ A,house ≥75 dB for the double roof. Because the outer roof had an additional function asa garden for the dwellings its total mass became around 800 kg/m2 (500 kg/m2 concrete and 300
kg/m2 soil-layers of the garden). Figure 3 also shows the transition of the roof at the connecting sidetowards the dwellings, where a dilatation with a vibration isolated mounting of the dwellings has
been designed and implemented.

Figure 3 – Detail of structural cross-section (side large pophall towards dwellings)

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Because of the high weight requirements for the inner roof of the pop halls as well as the demand
for a free span to reach sufficient interior height inside the halls, the interior roof was finally build
up using large, concrete T-beams with a height of 350 mm (small hall) and 500 mm (large hall).
These T-shaped beams were placed upside down and subsequently attached with steel reinforcementand finished with a flat upper side using poured concrete. This resulted in a structural thickness of
this interior roof of 450 mm for the small hall and 570 mm for the large hall. This build up can beseen in figure 3 and 4 where a detail of the interior roof/ceiling structure is given.

Figure 4 – Detail inner roof large pop hall (18 x 30 m).

Figure 5 – Detail inner roof small pop hall (12,5 x 24 m)

2.3 General lay-out of pop halls within the pop venue and dwellings on top
Both pop halls have been built as a fully separated heavy boxes of concrete on elastic bearings(<10 Hz) placed on columns in the basement. All around the concrete boxes of the halls a full268

separation is applied, see next figure 6 and 7. Figure 6 shows a ground floor plan of the 3-storey pop
centre with besides both pop halls also a café, foyers and a loading dock with a unique truckrotation lift.

Figure 6 – Ground floor plan of popvenue Doornroosje in Nijmegen (NL)
The walls of the boxes of the pop halls are of 300 mm concrete with a mass of 720 kg/m2, thefloors are 900 kg/m2 concrete and the ceiling/interior roof is at least 1,050 kg/m2. In between bothhalls is a corridor of 2m width. Towards the foyers deep door locks are applied and a free standing
dry-lining wall of 40 kg/m2 gypsum boards on 0.35 m air cavity filled with 0.15 mm mineral wool.
Under the floor a flexibly resilient suspended ceiling of 30 kg/m2 fibre board has been applied on
0.3m air cavity filled with 0,15 mm mineral wool.
In order to realize 100 4-chamber dwellings on the same footprint, these dwellings wereprojected in a ten storey high building above the three storey pop centre, as shown in figure 7 in across-section.

Figure 7 – Cross-section through building of Doornroosje, with dwellings above the pop centre

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2.4

Vibration isolated mountings

To realize a sufficient sound insulation from the cafe and the pophalls towards the dwellings andsimultaneously reducing railway vibrations an additional measure was taken by placing the totalbuilding of the dwellings on elastic bearings on the pop centre with a full dilatation in between, andby placing the dwellings aside from the pop halls as can be seen in figure 7. This isolated mountingof a complete 10 storey building required specific high pressure vibration insulated mountings to be
designed and implemented. Figure 8 shows a photo of the elastic bearings designed by CDM underthe dwellings. The elastic bearings applied have a resonance frequency below <10Hz and a 16 MPa
vertical loading capacity and consist of 4 layers of 20 mm rubber with 5 mm steel plates (size125x125x95 mm).

Figure 8 – Elastic bearings in position under dwellings on the pop centre during the construction phase
One of the requirements from the principal for using these elastic bearings under the dwellings
was that the pads could be interchanged at all times during the life of the building. For this reason asufficiently high void space (0.9 m height) was designed between the lowest floor of the livingbuilding and the concrete roof of the pop centre, such that the supports were reachable aftercompletion. Also a specific procedure for eventual replacement was designed by the supplier: In thedesign of the elastic bearings additional layers of high density fibre board were applied under thesteel-rubber bearings, so that these could be demolished by drilling through. Subsequently these
could be replaced by new rubber-steel pads that have been frozen under pre-stressed conditions.

3. MEASURING RESULTING SOUND INSULATIONS
3.1 Set up of equipment
Delivery measurements of the sound insulations had to be performed before the PA-system of thepop hall itself was present. Therefore a special set was hired, shown in figure 9.

Figure 9 – Measurement set up on the stage of the large pop hall with 18 subwoofers and 6 arrays
This measuring set consisted of 18 subwoofers and 6 array-speakers, that were being fed withpink noise for each separate octave band from 31 Hz to 4 kHz. The equivalent noise levels for eachseparately measured octave band are given in figure 10 and result in a equivalent pink noise level ofLAeq =125 dB(A) at the mixing desk.

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Sound levels in pophalls
Octave band noise level Lp (dB)

Doornroosje, Nijmegen (NL)
14013012011010090105 dB(A) house-spectrum
Mixing desk large hall during insulation test
Mixing desk small hall during insulation
test803163125250

500 1000 2000 4000

Frequency (Hz)Figure 10 – 105 dB(A) house spectrum compared with 125 dB(A) noise level with measuring set
Using the measuring setup mentioned above provided a sufficient signal-noise ratio inside thedwellings (>10 dB) up to 500 Hz octave band, and gave sufficiently reliable values for the main
predominant octave bands of the external sound insulation of the roof up to the 125 Hz octave band.
3.2 Resulting sound insulation of double roof and comparison with prediction
The resulting sound level differences D' of the double roofs (@1m) of both pop halls arespectrally given in figure 11. Using a standard substraction of 3 dB the resulting sound reduction
values measured become R' A,house =76 dB for the large hall and R' A,house =79 dB for the small hall. BothSound insulation of the roof of 2 pophalls
full fill the requirement of R’ A,house ≥75 dB.

Measured sound reduction D (dB)

Doornroosje, Nijmegen (NL)
10090
80
70
60
1m roof large pophall
1m roof small pophall

50403163125 250 500 1000 2000 4000
Frequency (Hz)Figure 11 – Measured D'(@1m) of pop hall roofs.
These measured octave band values for the sound reduction R' of the double roofs can begraphically combined and compared with the predicted spectral values, which is done in figure 1 and2 shown in the first chapter of this article.
From figure 1 showing the comparison for the large pop hall, it can be concluded that at thepredominant octave band of 63 Hz the value measured is about 3-4 dB below the predicted value(based on 15 dB/2f). This may partially be caused by the absence of damping (layers of mineral271wool) within this void, due to a practical consideration of the contracter only to implement mineralwool if proven necessary to meet the demands set. For the 31 Hz and 125 Hz band however thevalues measured are 3 dB higher than predicted. The differences between measured and predictedvalues above 250 Hz are mainly due to insufficient signal-noise ratio but are not predominant for thedifferences in the overall single digit value for the house music spectrum realized of R' A,house =76 dB
for the large hall, that full fills the requirement of R’ A,house ≥75 dB.
From figure 2, showing the comparison for the small pop hall, it can be concluded that at thepredominant octave band of 63 Hz the value measured is about 6 dB below the predicted value(based on 15 dB/2f). This may partially be caused by the similar absence of damping (layers ofmineral wool) within this void due to considerations mentioned above, but possibly also by the useof the void as a technical space (with several penetrations through the inner roof) and as a storage
with connecting light-weight walls etc. The differences between measured and predicted values
above 500 Hz are mainly due to insufficient signal-noise ratio but are not predominant for thedifferences in the overall single digit value for the house music spectrum realized of R' A,house =79 dB
for the small hall, that full fills the requirement of R’ A,house ≥75 dB but remains 4 dB(A) below thepredictad values of R’ A,house =83 dB.
3.3 Resulting interior sound level difference towards dwellings
Regarding the the interior noise transmission from the pop halls towards the dwellings the soundlevel differences measured are spectrally given in figure 12 and are at least D nT,A,house =99 dB and all
Sound insulation of pophalls to bedrooms
full fill the requirement of D nT,A,house ≥90 dB.
Measured sound reduction Dn,T (dB)

Doornroosje, Nijmegen (NL)
130
120
110
100
90
Large pophall to bedroom 3-310
Large pophall to bedroom 4-303
Large pophall to bedroom 1-307
Small pophall to bedroom 3-310
Small pophall to bedroom 4-308

8070603163125 250 500 1000 2000 4000
Frequency (Hz)Figure 12 – Measured D'n,T between pop halls and sleeping rooms of adjacent dwellings

4. CONCLUSIONS
Measured values of R'A,house=76-79 dB and D'nT,A,house=99 dB show that the prediction method used to predict
the sound reduction of double roofs proved its value and that the goals set for high sound insulations havebeen met in the pop Venue project of Doornroosje in Nijmegen (NL). However, further investigation isrecommended for subsequently fine tuning the prediction model for instance for the influence (absence orpresence) of mineral wool as damping material in the void between double concrete roofs.
A solid acoustic design proved to be of major importance to realize the sound insulation values
aimed for, as well as accurate construction, execution and surveillance during the building phase.
Having realized the sound insulations aimed for in these new venue plays an important factor in its
success. Doornroosje in Nijmegen is the first building in the Netherlands that shows that dwellings
can be build above pop halls, and the first where it showed possible to realize and prove a soundinsulation of D' nT,A,house ≥99dB to the dwellings by using a special setup with 125 dB(A) noise level.

REFERENCES
1. M. Luykx et. al: Pop venues in living areas. Proceedings of Euronoise 2015 Maastricht, p. 563-568.

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