Large numbers of American workers are exposed to high noise environments during their work days. Hearing loss from noise exposure is the most common occupational injury for American workers. Disposable viscoelastic foam earplugs are widely used to provide personal hearing protection. The ability of these foams to attenuate noise has essentially plateaued at the industry noise control reference, a Noise Reduction Rating (NRR) of 33 dB. While an NRR of 33 can be adequate for some environments, many people in industry and the military are commonly exposed to noise levels above 115 dB and impulse noises that can exceed 140 dB. Improvements in the sound attenuating abilities of commercially available viscoelastic foams would provide valuable improved hearing protection for people working in high noise environments. Low frequency attenuation, an inherent weakness of viscoelastic foams, especially needs improvement. Feasibility was demonstrated In Phase I, with Controlled Structure Foams (CSF) with significant improvement in overall sound attenuation (200 - 8000Hz) of over 3 dB and in the low frequency area (under 1000Hz) of over 4 dB. This was achieved using common foam manufacturing techniques fine-tuned to create a new foam structure. At a given noise level this attenuation offers more than a 40% improvement of time of protection. This new class of foams will be optimized and manufactured into viscoelastic foam earplugs with a major partner and also converted into foam ear tips to enhance hearing/communicating-in-noise devices. This Phase II project will further develop the CSF technology by meeting 3 objectives: Optimize the Controlled Structure Foam to achieve the best attenuation, user comfort, and sealing in the ear canal. Prove, with our preferred manufacturing partner, optimized Controlled Structure Foam for improved attenuation viscoelastic foam earplugs can be easily and economically produced. Utilize this Controlled Structure Foam to make various ear tips for our many partners'hearing/communicating-in-noise audio devices.
Noise related hearing loss is one of the most prevalent occupational health concerns in the United States with many millions of Americans exposed to hazardous noise levels every day. Foam earplug and foam ear tip hearing protectors are popular but improvement is needed to provide more and/or longer times of protection in high-noise industrial, military, and transportation environments. Success with this research will improve sound attenuation at all frequencies, especially more challenging lower frequencies (higher energy), resulting in more effective foams reducing the incidence of hearing loss - the most common industrial injury.