IL CALCULATOR

Calculate insertion loss for barriers, enclosures, and silencers.

Barrier

Source Height (m)

Receiver Height (m)

Barrier Height (m)

Source to Barrier (m)

Barrier to Receiver (m)

Barrier Results

Path Difference δ:

0.332 m

Fresnel N @ 1 kHz:

1.94

IL @ 500 Hz:

13.5 dB

IL @ 1 kHz:

16.2 dB

Enclosure

Wall TL (dB)

L (m)

W (m)

H (m)

Internal Absorption α

Enclosure Results

Surface Area:

16.50 m²

Room Constant R:

38.50 m²

Effective IL:

23.5 dB

IL is reduced from wall TL due to internal reverberant buildup.

Lined Duct Silencer

Silencer Length (m)

Duct Width (m)

Duct Height (m)

Lining Thickness (m)

Lining α

Silencer Results

IL @ 500 Hz:

3.1 dB

IL @ 1 kHz:

3.7 dB

IL @ 2 kHz:

3.7 dB

Dissipative silencers are most effective at mid-high frequencies.

Insertion Loss vs. Frequency

Blue: Barrier IL increases with frequency (Maekawa formula)

Green dashed: Enclosure IL (frequency-independent approximation)

Orange: Lined duct silencer IL (peaks at mid-frequencies)

Typical Barrier IL Values

Barrier Type	IL Range
Highway noise barrier (3-4 m)	5-10 dB
Industrial barrier (close)	10-15 dB
Building as barrier	15-20 dB
Theoretical max (single edge)	~24 dB

Design Guidelines

Barriers: Position barrier close to source OR receiver for maximum δ. Avoid gaps at ends (flanking).

Enclosures: Add internal absorption (α ≥ 0.7) to prevent reverberant buildup. Seal all gaps.

Silencers: Increase length for more IL. Consider pressure drop and flow noise at high velocities.