The procedure for planning a VAS requires experience in electroacoustics. The following example shall show you some aspects for such a planning. It illustrates a supermarket with the below specifications:
|Zone 1 - 6||Size||Type||Height|
|Sales area 1*||1 AB||1547 m2||Trapezoid sheet||6 m|
|Sales area 2*||2 AB||1547 m2||Trapezoid sheet||6 m|
|Adjoining rooms||3 AB||257 m2||Acoustic ceiling||3 m|
|Warehouse||4 AB||287 m2||Smooth concrete||3 m|
|Catering / WC||5 AB||190 m2||Acoustic ceiling||3 m|
|Technical rooms||6 AB||37 m2||Smooth concrete||3 m|
* Sales area split into two virtual fire compartments (Sales area 1 & Sales area 2)
Transmission of background music to selectable zones (5 areas divided into 6 zones)
1 remote microphone for manager’s office
3 paging microphones for cashiers
Emergency functions: Automatic and manual voice alarm, emergency microphone in the equipment room
In accordance with EN 60849 (EN 50849) the emergency SPL must be at least 6 – 20 dB above the ambient noise level (10 dB was chosen in the example) and the speech intelligibility must be greater than STI 0.5.
In comparison to most speaker types pendant speakers can be mounted on trapezoidal sheet ceilings. In addition these can be installed closer to the audience providing better speech intelligibility. Choice of EN 54-24 speaker: PE-154EN
The acoustic ceiling allows an easy installation of ceiling speakers. Since some of these rooms are to small for more than one speaker, an A/B speaker is most suitable and complying with EN 60849 (EN 50849) or TS 54-32. Choice of EN 54-24 speaker: PC-245AB-E
Since the ambient noise in the warehouse is higher than in the sales area, loudspeakers with a higher SPL are neccessary. The fixation requires only one or two screws. Choice of EN 54-24 speaker: CS-154EN
Catering / WC:
The acoustic ceiling allows an easy installation of ceiling speakers. Choice of EN 54-24 speaker: PC-2369EN
Typically the ambient noise in technical rooms can be high. Therefore a reflex horn speaker is a good solution. Choice of EN 54-24 speaker: SC-615BS
Due to the size the sales area is the most critical sector according to the speech inteligibility. The application of the sound simulation Ease Evac software can support finding the final speaker locations for obtaining the required SPL and STI. Starting with a first idea of speaker distribution, the simulation result gives a hint how to improve the distribution. An iterative process of change and resimulation leads to an optimum result.
An important value for the speech inteligbility calculation is the reverberation time. In the supermarket example it is 1.5 s in the sales area.
Average STI 0.56 / STI 0.52 (minus standard deviation)
|EN 54-24 loudspeakers|
|Quantity||Model||Height||Tapping|| Total dB SPL|
|Sales area 1||28||PE-154EN||4,5 m||10 W||94||280 W|
|Sales area 2||28||PE-154EN||4,5 m||10 W||94||280 W|
|11||PC-245AB-EB||3 m||2 x 3 W||88||66 W|
|Warehouse||4||CS-154EN||2,5 m||10 W||97||40 W|
|Catering / WC||10||PC-2369EN||3 m||3 W||95||30 W|
|2||SC-615BS||2,5 m||3 W||108||6 W|
|Total load of the 6 A/B loudspeaker circuits:||702 W|
All required functions can be fulfilled by the VM-3000 system.
Up to 60 zones, can be controlled individually for background music
4 remote microphones
3 audio inputs for paging microphones, e.g. PM-660D
Integrated voice storage function for automatic and manual voice alarm as well as integrated emergency microphone on VM-3360VA
Using system manager VM-3360VA and expansion amplifier VM-3360E enables 6 A/B loudspeaker circuits with an adequate total amplifier power of 720 watts.