Wednesday, 27 September 2017

Sorry to Hear That

Aaagh not another dodgy report?
The RCS noise report that accompanies the planning application looks pretty technical, so we asked a helpful acoustic expert (HAE) to cast an eye over it:

GLERA: You've read through the report, it seems to say that the school playground won't cause any disturbance for residents.

HAE: Hmmm...

GLERA: Hmmm what? Is there something we should know?

HAE: It estimates that the nearest sound receptors are “about 25m to the South”. In fact Basterfield house windows are 8.8m away from the playground.

GLERA: And that's important because?

HAE: Distance is the main form of attenuation of the noise from the playground - perimeter fencing won't have any effect for the first floor windows and above - its line of sight.

The assessment levels they have used are not correct (table 8.1). By definition,  the levels in policy (LOAEL/SOAEL) are absolute levels and not variable.

GLERA: They make the following assumption from similar playgrounds: "At the edge of an external play area with a similar number of pupils, noise level was found to be around 75 dB LAeq,1h."  Is this realistic?

HAE: Yep. Now ask about Ambient Noise.

GLERA: What about Ambient Noise? That's the background level at our windows now right?

HAE: Yes, The report assumes the Typical Ambient Noise Level (LAeq,9h) to the South is 65dB, which seems unlikely. Their own survey within the Estate boundary gave readings of between 50 and 54 dB (Table 4.3) No acoustic survey was undertaken to the South of the site (Basterfield) which is the most directly affected, but it most closely resembles the location to the West.

GLERA: How do we check?

HAE: Here, borrow one our sound meters. Check the background noise at different times of day

GLERA: Anything else?

HAE: Give it back when you're done.

We checked the typical (Ambient) noise levels at Basterfield House. they hovered around 50-55 decibels in the mornings, went down slightly in the afternoons. Here's what we found out:


RCS Noise Report 2 from Charles Humphries on Vimeo.

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