City to add new sound monitoring for 2018 SnowGlobe

Sound levels from SnowGlobe have been a concern of many residents in South Lake Tahoe, and after a presentation at Tuesday's City Council meeting, new sound monitoring protocols will start this year.

After Recreation Superintendent Lauren Thomaselli gave the SnowGlobe Special Event Agreement Annual review, staff decided to perform the sound measurement for the 2018 festival in both A-Weighting and C-Weighting.

In 2011, the first year of SnowGlobe, there was no sound monitoring. In response to community input, City staff measured the sound monitoring in A-Weighting during the 2012 to 2017 music festivals. The Occupational Safety and Health Administration (OSHA) recommends sound measurements in A-Weighting, which is the standard that the City applied to sound monitoring between 2012 and 2017.

But, with complaints continuing about the type of sound that makes in through neighboring residential areas, C-Weighting is going to be added.

Frequency Weightings:

The human ear responds more to frequencies between 500 Hz and 8 kHz and is less sensitive to very low-pitch or high-pitch noises. The frequency weightings used in sound level meters are often related to the response of the human ear, to ensure that the meter is measuring pretty much what you actually hear.

It is extremely important that sound level measurements are made using the correct frequency weighting; usually A-Weighting. For example, measuring a tonal noise of around 31 Hz could result in a 40 dB error if using C-Weighting instead of A-Weighting.

A Weighting:

The most common weighting that is used in noise measurement is A-Weighting. Like the human ear, this effectively cuts off the lower and higher frequencies that the average person cannot hear. A-Weighted measurements are expressed as dBA or dB(A).

C Weighting:

The response of the human ear varies with the sound level. At higher levels, 100 dB and above, the ear's response is flatter, as shown in the C-Weighted Response to the right.

Although the A-Weighted response is used for most applications, C-Weighting is also available on many sound level meters. Ir is usually used for Peak measurements and also in some entertainment noise measurement, where the transmission of bass noise can be a problem.