Perforated Acoustic Metamaterial (PAM)

Overview

Perforated Acoustic Metamaterials are intended for use where the flow of air is a requirement for effective operation of the equipment generating the undesired noise.  A classic example would be a compressor requiring air for cooling in operation operation but also generates undesirable sound levels.

Upon receiving a noise profile from your team, our engineering team will design an acoustic panel and develop a membrane solution specific to your application.

How It Works

  • Air flow through orifices in constraint sticks
  • Vibrations of membranes counterbalance sound waves passing through orifices
  • Vibrations of membranes induce local turbulence to enhance heat transfer

Applications

Refrigerator Noise Reduction

In 2016, we invented the cooling and sound-insulation baffle which is applied on the compressors of refrigeration appliances. The baffle is designed for the noise energy concentrated frequency band of the compressor and reduces the noise peak value by 12 dB. The whole sound insulation level is increased by 6 ~ 10 dB than that of the original grid plate. Moreover, the baffle does not affect the normal heat dissipation or increase the working energy consumption of the compressor.

In the evaluation band (280 Hz to 800 Hz), the sound insulation of PAM-400 is close to that of a uniform steel plate with the thickness of 1.5 mm , 3.1 dB lower than the grid plate, and 4.0 dB lower than the grid plate in the human ear sensitive band of 20-10kHz. It significantly reduces the radiation noise of the refrigerator.

Figure: PAM
Figure: Uniform Plate
Figure: Grid Plate
Figure: Without Plate
Data Collection
Frequency (Hz)
Without plate (dBA)
Grid Plate (dBA)
Uniform Plate (dBA)
PAM-400 (dBA)
280-800
36.1
34.5
31.7
31.4
Minus without plate
-1.6
-4.4
-4.7
20-10k
42.9
40.0
34.4
36.0
Minus without plate
-2.9
-8.5
-6.9

Case Studies

PAM vs. Grid Plate

The common solution to containing noise is using a plate made of various materials which has holes of various shapes – this “Grid Plate” is not nearly as effective as using our Perforated Acoustic Material. The images on this page and the video file provided show the results of PAM – Contact us today so our engineers can work on solving your noise problem.

Figure 1: 85.8 dB, No PAM Applied
Figure 2: 75.6 dB, PAM Applied
Figure 3: 82.7 dB, Perforated Plate Applied
Figure 4: Perforated Plate, 1.7 km/m2
Figure 5: PAM, 1.4 kgm2
Chart: Sound Transmission Loss

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