## Open versus closed ventilation devices – what is the impact on indoor sound pressure levels?

Sigmund Olafsen, siv. ing.

Brekke & Strand akustikk AS

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Norwegian regulations regarding indoor sound pressure levels have been in force since 1997. In existing residences exposed to existing noise sources the regulations state that indoor levels shall not exceed an LAeq,24h of 42 dB. The responsibility of sound reduction measures lies with the owner of the noise source. The regulation states that the indoor level is derived assuming closed windows and closed ventilation devices.

A change in the regulation is now being evaluated. It would be more realistic to assume open ventilation devices. Earlier studies have indicated that the critical cases are situations where the ventilation devices face the noise source directly. The presented investigation has concentrated on the difference in indoor levels for two types of ventilation devices common in older houses. Calculations are based entirely on empirical data. The types of noise sources considered are roads, railways, trams and subways, two situations for each source. Five general types of houses of typical Norwegian construction are considered.

The paper will present the reported results from the calculations based on field data and considerations on the validity of the methods.

The Norwegian Pollution Control Authority has commissioned the work, and has permitted the results to be presented at BNAM.