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Enclosure & Barrier TL

A panel blocks sound roughly in proportion to its mass: doubling the mass or the frequency buys 6 dB. The important part is the second calculation — an enclosure is only as good as its worst hole. One percent open area caps a 40 dB enclosure at about 20 dB, which is why sealing matters more than adding mass.

Panel surface density (kg/m²)

Frequency (Hz)

Panel area (m²)

Gap / opening area (m²)

Gap TL (dB, 0 = fully open)

Panel TL (mass law)

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TL one octave up

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Composite TL with the gap

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Lost to the gap

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Open area

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TL at double the mass

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Mass law is a ceiling, not a promise: real panels lose performance at their coincidence dip and at low frequency. Absorption inside the enclosure is a separate effect that stops it becoming a reverberant box.

A helper, not a substitute for engineering judgment. Verify against the governing standard.