Technology · Engineered with Absora Technology

HSA3 – sound absorption made of metal, without mineral wool

The heart of every ForCoTech enclosure: a patented acoustic meta-metal by ABSORA GmbH, Berlin. It damps precisely the low tones of compressors and fans, is non-combustible and withstands wind and weather for good.

Configure an enclosure with HSA3 Request the test report

Schematic section through HSA3: corrugated micro-perforated face layer, air chambers, spring-mounted intermediate layer, resonance cavity and carrier plate

up to −60 %pressure drop vs. splitter silencers

approx. +30 %absorption at 125–250 Hz, EN ISO 354

A1non-combustible to EN 13501-1

0 fibresno mineral wool, no foam

What is HSA3?

A metal that swallows sound – through its shape

Classic absorbers rely on mass and fibres: mineral wool or foam, as thick as possible. HSA3 takes a different route. As an acoustic meta-material it draws its effect from geometry – from many small, precisely tuned chambers, holes and springs.

HSA3 was developed and patented by ABSORA GmbH in Berlin. Silent Engineering has used it for years as the standard in all ForCoTech and Silent-Mode enclosures – as inner lining, as tube silencer and as partition wall.

The result: a lining that also damps low tones, does not burn, does not absorb water and offers the air less resistance than conventional splitters.

Schematic: sound hits a corrugated, micro-perforated sheet mounted on springs on a carrier plate — **Air and springs instead of mineral wool** – sound passes through the holes, air and intermediate layer vibrate, energy turns into heat.

Schematic: HSA3 partition between two air-to-water heat pumps keeping the moist defrost air of one unit away from the other — **HSA3 as a partition** – decouples two heat pumps acoustically and keeps defrost air away.

Working principle

Three mechanisms in one layer

For HSA3 to work across a broad frequency range – from the compressor's hum to the fan's rush – several physical effects work together.

Helmholtz resonators

The micro-perforated face layer forms many small resonators with the air chambers behind it. Air rubs in the fine holes – sound energy turns into heat.

Mass-spring system

The spring-mounted intermediate layer vibrates with the air in the cavity. This system is tuned to low frequencies, where porous absorbers would have to be very thick.

Impedance step

Between front and rear chamber, a deliberate difference in phase and sound pressure arises. This step creates additional absorption; the multi-layer core dissipates the rest.

Key data

What HSA3 measurably does better

Parameter	HSA3	Evidence
Sound absorption 125–250 Hz	approx. +30 % absorption	reverberation room test to EN ISO 354, test report on request
Pressure drop	up to 60 % lower than conventional splitter silencers	per project by CFD simulation
Reaction to fire	A1, non-combustible – the highest class	classification to EN 13501-1
Tube silencer Ø 200 mm	tuned to 63–250 Hz, loss coefficient ζ ≈ 0.3 per row, approx. 1.6 kg/m	design values
Example acoustic pack (380,000 m³/h)	−18 dB(A) sound power at around 21 Pa pressure drop, 13 kg/m² envelope	reference design, prediction – details
Effect on site	level reduction at the receiver	on-site differential measurement after installation

Compared with classic absorbers

Property	Mineral wool	Foam (PE/PU)	HSA3
Principle	porous, friction in fibres	porous, friction in cells	resonators and mass-spring system
Low frequencies	only with great thickness	only with great thickness	specifically tuned, at low thickness
Reaction to fire	non-combustible, depending on product	combustible, flame-retardant as FR version	A1, non-combustible
Moisture, rain	absorbs water, needs covering	depends on cell structure	unaffected, metal
Fibres, abrasion	fibres, cover fleece needed	no fibres	no fibres
Pressure drop in splitters	reference	comparable	up to 60 % lower
Dismantling	mixed waste	plastic waste	bolted, separable by material

General properties of the material groups; individual products may differ. Test report and technical documents for HSA3 on request: info@forcotech.com. As an alternative we can use Stratocell® Whisper® 50 mm FR on request.

Applications

Where HSA3 is used in our solutions

Inner lining

Acoustic enclosures

All walls and roofs of our enclosures are lined with HSA3 – from the H-Series to the large enclosure.

Heat pumps & AC →

Silencer

Tubes Ø 200 mm

Tubes with internal resonance chambers in the air outlet, tuned to 63–250 Hz. Rounded leading edge, very low pressure drop.

Chillers & large heat pumps →

Partition

Between units

Decouples neighbouring units acoustically and in terms of air flow – levels do not add up, exhaust and defrost air stay separate.

VRF/VRV →

Absorber

Noise barriers

On the unit side, HSA3 stops the barrier from reflecting sound back or sideways.

Noise barriers →

Fire safety

Battery storage

Non-combustible A1, no fibres – the right choice wherever nothing may burn along in a fire.

Inverters & BESS →

Retrofit

Single noise sources

Compressor panel against low-frequency droning, fan cylinder against the blade-passing tone – close to the source, individually removable.

Modular kit →

Engineered with Absora TechnologyHSA3 was developed by ABSORA GmbH, Berlin, which holds the patent. Silent Engineering handles design and acoustic engineering; manufacturing and installation are carried out together with ABSORA – design and execution from a single source.

HSA3 in your enclosure

Every enclosure from the configurator is lined with HSA3. Enter your unit, get a guide price.

Open configurator All solutions

Frequently asked questions about HSA3

What does “acoustic meta-material” mean?

Meta-materials get their properties not from the material itself but from their structure. In HSA3 these are periodically arranged chambers, holes and springs that are tuned to the frequencies of compressors and fans.

Why does HSA3 have less pressure drop than classic splitters?

Porous splitters must be thick to work at low frequencies and therefore narrow the free cross-section. HSA3 achieves its effect at low component thickness – more area is left for the air. Compared with conventional splitter silencers, pressure drop falls by up to 60 %.

How are the values verified?

The absorption of HSA3 was tested in a reverberation room to EN ISO 354. For every project we calculate a noise prediction in advance; after installation an on-site differential measurement proves the actual effect.

Can HSA3 withstand rain, frost and UV?

Yes. HSA3 is a metal, weatherproof and designed for permanent outdoor use, where heat pumps and chillers stand. It does not absorb water and contains no fibres that could shed.

Is HSA3 suitable for units with R290?

Yes. As a non-combustible A1 material, HSA3 meets the requirement for the inner lining of enclosures around propane units. The enclosure itself must also be floorless and approved by the unit manufacturer.

Can HSA3 be used without a full enclosure?

Yes. Because HSA3 is modular, individual noise sources can be treated specifically, such as the compressor compartment or the fan. This saves space and material and is well suited to retrofits.