Usually when a “pre-operational sound report” of an activity or dwelling is carried out, we calculate the airborne sound, impact sound, reverberation and noise transmission outside and inside by means of software or calculation templates.

Whenever the time comes to calculate impact sound, we encounter many problems.

1. Calculation software is costly and unintuitive

2. You have to read ISO 12354 standard

3. You do the calculations and you get odd results

4. When you have to calculate the impact sound reduction from a room below to a room above, there is no calculation method according ISO 12354.

So how do you calculate it?

Solution: Well, this is when you see pre-operational reports and noise impact isn’t calculated (an easy solution).

QUICK GUIDE TO IMPACT SOUND CALCULATION

When calculating impact sound in buildings, we always come across two cases:

A. The noise-emitting room is above the receiver

B. The noise-emitting room is next to the receiver

Both cases are described in Standard UNE -EN 12354-2:2001

However, the standard isn’t taken into consideration when the impact comes from below and the receiver is above.

This and other case studies are well documented in German standard DIN 4109, which, although not applicable in the rest of the world, can help us to resolve calculation issues.

If we calculate according to the “simplified method” described in standard UNE EN 12354-2:

1. Weighted Normalized Impact Sound Pressure Level: of homogeneous slabs within a range 100 a 600 Kg/m2 surface mass (m`).

**Ln, w, eq = 164 – 35 lg (m’), (dB)**

2. Impact sound reduction index, with the dynamic stiffness by surface unit (MN/m3) and the surface density of the floating floor (Kg/m2), we get the ∆Lw index from Annex C of the Standard

Or from reliable technical files

dBimpact

1. Correction K for indirect transmission, knowing the average density of the side elements not covered with elastic layers and the surface density of the floor covering/slabs m` (kg/m2), we move to Table 1 of point 4.3.1 of the Standard to obtain the value K (dB).

**K Correction for indirect transmission in decibels**

If one or more large-scale sidewall constructions are covered with additional coverings (wall facings) with a resonance frequency f_{o}< 125Hz according to chapter D.2 of Standard EN 12354-1:2000, the surface densities of the covered elements do not take into account the calculation of the values of average mass

If one or more large-scale sidewall constructions are covered with additional coverings (wall facings) with a resonance frequency fo< 125Hz according to chapter D.2 of Standard EN 12354-1:2000, the surface densities of the covered elements do not take into account the calculation of the values of average mass

2. Weighted Normalized Impact Sound Pressure Level L`nw:, the prediction of acoustic pressure is made from the weighted values of the elements according to the procedures of Standard EN ISO 717-2:2013, and its application is limited to enclosures located one on top of the other, with homogenous floor covering using the formula:

**L’n, w = Ln, w, eq – ∆Lw + K** , (dB)

At this point we can now calculate the cases of impact from above to below perfectly and with the detailed method in addition to this one, we could do so vertically.

But what happens when the impact is from below to above, as in the case of a noisy activity like a restaurant or café underneath housing?

How can we do a good prediction without either under- or over-estimating?

For this particular case and others, the German Standard DIN 4109, defines the same value L`n, w, but adds a KT value, depending on the spacial distribution of the enclosures and the building systems; so creating a relationship between excitation point and propagation.

Adding this value to the formula, we can obtain:

**L’n, w = Ln, w, eq – ∆Lw + K – Kt** , (dB)

If you want to obtain the calculation template, tell us what you want to calculate and we can help you with some of our impact solutions

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