## Model for predicting the annoyance risk from external low frequency noise inside a building

Jukka Keränen, David Oliva Elorza, Vesa Koskinen, Valtteri Hongisto

Finnish Institute of Occupational Health, Indoor Environment Laboratory,

Lemminkäisenkatu 14-18 B, 20520 Turku, Finland

jukka.keranen@ttl.fi

Inside Finnish dwellings and schools, A-weighted noise levels caused by external noise

sources shall be below 35 dB at day time and below 30 dB at night time. In offices, the Aweighted

daytime level should be below 35 dB in meeting rooms and below 45 dB in work

rooms. Similar requirements apply in most European countries. In certain situations,

external noise can contain low frequency noise (LFN) in such a degree that the risk of

annoyance should be considered separately. In such cases, current knowledge and

accuracy of engineering is not sufficient. The requirements for LFN levels are not

harmonized between countries, sound insulation data of facade components is not

available below 100 Hz, and measurement methods of LFN level inside a room are

controversial. The aim of this study is to present an engineering model which can predict

the possible variation of the LFN level inside a room from an external sound source. The

prediction requires the outdoor noise level in front of the facade, the sound reduction index

of the facade, and the sound absorption area of the room. The essential contribution of the

model is that it takes the important uncertainties into account. They appear in the

measurement of outdoor noise level, sound reduction index and indoor noise level. The

predicted indoor noise level is presented with variation range and compared to

requirements for LFN level. The results are easy to inspect and enable objective risk

assessment for low frequency noise annoyance. The model includes the third octave

bands from 20 to 5000 Hz. The model is demonstrated by using the emission of road

traffic noise.