Sound Insulation Test on Recycled Carpet for ECOI-NW Project

The LJMU Applied Forensic Technology Research Group was approached by Scott Caldwell and Hazha Mohammed from LJMU’s ECOI-NW Project, who advised that they were dealing with a flooring company that reused/ recycled Carpet tiles for domestic use for housing. The group required the sound insulation of these tiles to be tested. The AFTR group was given a 50 cm x 50cm square, 5mm thick sample of carpet tile to test.
A sound test was conducted in a sound isolation booth using a laptop with Steinberg Cubase Pro 12 to trigger test sounds. The laptop was connected to a Focusrite Audio interface and a KRK VXT4.
Powered Speaker. A Behringer ECM 8000 reference Microphone was used and placed 1m away from the speaker cone. Acoustic baffles were placed around the sound booth windows and the microphone. A Eurisem EP 626 Sound level meter was calibrated at 94 dB before the white noise test tones were played on Windows Media Player. The white noise test tones were played and recorded first without the Carpet, then with the Carpet suspended off the floor, directly in front of the microphone capsule.
White Noise Results
White noise test results showed that the carpet tile has little sound reduction in the 20 Hz to 700 Hz frequency range. However, at 2 kHz there is a significant reduction of -14.4 dB, with a drop in level until reaching 8 kHz at an impressive -32.9 dB, continuing to drop until over 20 kHz..
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It is well understood that regarding sound absorption material, the thicker the material, the lower the effective frequency range is. The test carpet sample given is reasonably thin, so it will only be effective in absorbing mid-range to higher frequencies, as evidenced in Chapter.3 These Carpet tiles absorb the most frequencies from 2kHz to 8kHz, which will be helpful as these are some of the frequencies that humans hear best. The test carpet does not absorb many lower frequencies under 2 kHz. It is reasonable to assume that a carpet with a thicker underlay would be better at blocking lower frequencies