Tackling tricky acoustics from the poolside

Swimming pools are notoriously tricky spaces when it comes to providing intelligible sound. G-Sound tackles the Olympic sized Aqua Sport Center.

Situated in the western Hungarian city of Gyor,  the  Aqua  Sport  Center  has  been described as the most modern  sports centre in the country.  

The  building  features  a  50x25-metre Olympic sized swimming pool with a viewing area comprising 800 fixed seats and capacity for  an  additional  400.  Ancillary features  include  a  16x10-metre  educational  pool,  two  saunas  and  plunge  pool, jacuzzi,  relax  room,  ï¬tness  rooms  and changing rooms. 

The venue required a sound system to provide  good  intelligibly  in  the  reverberant space  and  local  integrator  G-Sound  was  chosen  to  handle  the  project.  The company’s  owner  József  Gricz   wrote  the  specifications  for  the  project,  which were  accepted  by  the  pool  management,  and  conducted an electro-acoustical simulation. 

Gricz specified RCF equipment for the project  and  worked  with  the  manufacturer’s Hungarian  distributors  Chromasound  to  deliver them. 

He  based  his  system  design  around ten RCF  P4228 indoor/ outdoor,  weatherproof (IP55- rated) wide-dispersion, two way  loudspeakers.  

Imre  Makkay  from  Chromasound  explained:  “Our target was to achieve as good as possible  STI from the budget in this special environment,  and of course the IP rating because of the pool  operation. We had to reproduce sound accurately  in  all  areas, not  only  for  the  spectators,  but  the  coaches  and  the  competitors  on  the starting blocks.  

“The  budget  was  limited,  and  we  need  to  produce  high  SPLs  even  good tonality  mainly  for  spoken  words  and  for  jingles,  spots  and  background  music. The  water  recirculation  and  the  air  handling  unit  is  always  operated  on  66  dB LAeq  level,  so  the  system  needs  to  produce  minimum 20 dB more on every seat.” 

He continued: “There are three main grandstands  around the pool. On the longitudinal side, we’ve  installed four speakers, and further units installed  on each end of the room. There’s a sitting and  standing  VIP  area  in  one  of  the  corners,  on  a gallery, with  two  further  speakers.  The  speakers  are  hanging  above  the  water  surface, installed  horizontally underneath the electrical cable trays  on our custom-designed stainless steel consoles.” 

Gricz added: “We’ve defined distances from the  seats to the speakers, mindful of the horn’s 110° x  60° dispersion angles.” 

The  speakers  are  divided  into  ï¬ve  zones,  and  with  a  dedicated  DX4008  4-in/8-out  digital  system controller installed in the technical room,  there are free I/O’s for future needs. 

Each half of the pool area is served by its own amplification rack positioned close to the speakers  in order to shorten the low impedance cable runs.  The system is driven by a total of five RCF IPS  3700  stereo  amps,  delivering  up  to  2  x  1500W RMS@4Ω.  

The  challenges  faced  by  G-Sound  and  Chromasound were all the result of the many fl at  surfaces  (glass,  water,  and  walking  areas),  and  with minimal acoustic treatment, the average time  decay was 4.5 sec. 

Makkay explained: “After the fine tuning which  was done by measuring and listening experiences,  the  Speech  Transmission  Index’s  average  was  measured  as STIPA 0,48  at  normal  conditions  (all zones operating for empty grandstands), and  STIPA 0,41 at worst conditions (all zones operating  for  empty  grandstands  beside  the operation  of  building  automation).  This  has  fulfilled  our  expectations.”    

RCF amplifiers,  loudspeakers and  output digital processors 

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