Low frequency noise is often described as rumbling or droning noise.  It can be generated by machinery such as:

• pumps
• compressors
• diesel engines
• fans
• generators
• boilers.

Low frequency noise can also be produced by natural sources. This includes wind, wind effects on structures and thunder.  Electrical appliances in homes and buildings, such as refrigerators and air conditioners, can emit low-frequency noise.

In EPA’s guidelines, low frequency noise is defined as noise with significant acoustic energy in one-third octave bands ranging between 10 Hz to 160 Hz.  Similar to the octaves in music, an octave band is a division of the frequency range. This  can be used to analyse the frequency spectrum of the measured sound.  Each octave band is divided in three one-third octave bands. This allows investigating the sound with a more detailed resolution.

Health impacts from low frequency noise

Low frequency noise can affect people in the same way as other types of noise.  This can include:

• sleep disturbance
• annoyance 
• impaired task performance 
• daytime tiredness
• disturbed daily cortisol pattern due to stress.  

These effects can cause some people to experience nausea and headaches. 

Noise assessment 

The human range of hearing is often described as being from 20 Hz to 20,000 Hz (20 kHz). However, low frequency sound at frequencies less than 20 Hz can be audible by some.  Its audibility depends on the sound pressure level measured in decibels (dB). It also depends on the hearing sensitivity of whoever can hear it. Low frequency noise is sometimes reported  as a perceived vibration that travels through the air. It can also be reported as a pulse or pressure in the ears or a vibration felt in the chest or the ear.

Investigating and addressing low frequency noise can be complex.  It requires specific measurement and assessment procedures. Unless the source is clearly identified, it can be difficult to find out what causes low frequency noise.

It is not possible to completely suppress low frequency noise within any natural environment.  EPA’s role is to investigate low frequency noise issues arising from a commercial, industrial or trade premises within the environment and potentially having an adverse effect on community. EPA investigates and addresses the key elements of the noise by determining:

• source
• emission types and occurrences 
• frequency ranges 
• sound pathways and receptors 

These investigations are conducted so far as reasonably practicable to remediate the issue (if required).

More information

• 1996: Noise Guidelines: assessing low frequency noise
• Report noise pollution.