Evaluation of low-frequency façade insulation down to 20 Hz; measurement of low-frequency façade insulation down to 20 Hz and subjective assessment of synthesized cruise ship noise
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Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Modellbyggare
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Sammanfattning
Low-frequency noise has become a growing concern due to its potential adverse effects
on human health. However, existing measurement standards and calculation
software typically do not cover frequencies below 50 Hz, despite the human hearing
threshold extending down to 20 Hz. The knowledge gap regarding sound insulation
in the lower frequency range has prompted the need for further research. Recent
regulations allow for industrial noise to exceed permissible levels near dwellings as
long as indoor requirements are met, creating opportunities for construction in previously
unsuitable areas. An example of such a location is Värtahamnen in Stockholm, where
cruise ships regularly dock and generate noise from their ventilation systems and
onboard electricity generation. These ships are expected to produce low-frequency
noise that may pose challenges for nearby planned dwellings. This raises questions
about evaluating low-frequency sound insulation and establishing reliable
measurement methods, considering that sound pressure levels within rooms
can vary significantly due to room modes.
This thesis utilizes a field-tested measurement method to assess the sound insulation
of façades down to 20 Hz. The measurements also include a subjective assessment of
synthesized cruise ship noise and its perception by the auditory system. Additionally,
a finite element model was utilized to analyze room modes and gain further insights
into their influence on the acoustic environment.
The results of the measurements indicate that common façade structures exhibit a
moderate sound insulation capability down to 20 Hz. Among the various parameters
that affect sound insulation below 100 Hz, room modes and windows were found to
have the most significant impact. The subjective assessment revealed that when the
synthesized cruise ship noise is barely audible in the receiving room, its frequency
contents below 80 Hz lie below the human hearing threshold; however, as the noise
levels increase to the point of being disturbing, this frequency limit is lowered to 31,5
Hz. These results indicate that modern façades may have adequate sound insulation
below 50 Hz considering the human hearing threshold. However, achieving this
requires careful planning and construction.
Beskrivning
Ämne/nyckelord
low-frequency noise, room modes, façade, hearing threshold, level differ ence, measurements, dwellings