Dr Sean Smith, building acoustics research fellow at the BPC, said the survey showed the introduction of the Ctr unit of measurement would force housebuilders to improve protection against low-frequency sound, such as music bass notes. However, the use of the Ctr rating in acoustic testing would lead to less protection against medium- and high-frequency sounds, such as speech.
The survey also found that using this type of sound testing will favour some construction methods, such as masonry cavity and solid walls, which naturally offer better protection against low-frequency sound.
The BPC assessed the effects of the Ctr rating by converting test results on hundreds of dwellings using the Ctr yardstick. The occupants of the buildings were asked to rate the sound performance of walls and floors.
Many complaints relate to bass notes in music. We want a rating that would take more account of this
Office of the Deputy Prime Minister
In dwellings where walls and floors met the new minimum requirements for airborne sound insulation, only 15% of respondents thought it was satisfactory. And in tests where walls and floors met minimum standards in converted buildings, for which regulations are less onerous, not one respondent was satisfied.
The government said it was meeting concerns about low-frequency music but admitted anomalies existed. A spokesperson for the Office of the Deputy Prime Minister said: "Many complaints about noise relate to bass notes in pop music. We wanted a method of rating sound insulation that would take more account of this.
"The Ctr rating was first intended for traffic noise and is not ideal. BRE has assessed its performance on its database of sound insulation and found it to perform well. There are some anomalies, but this will happen with any single figure index because they are a simplified way of expressing complex information."
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