SBIR-STTR Award

Viscoelastic foam earplugs are commonly used for personal hearing protection to help reduce the incidence of hearing loss;however, many work environments exist where the protection from currently available earplugs is insufficient. In addition, the ability of existing foam earplugs to attenuate low frequency energy is relatively poor. Pilot experiments were able to produce viscoelastic foam constructions of substantially higher controlled structure than believed to be found in currently available viscoelastic foam earplugs. Even with minimal optimization, this structure contributed to substantially higher overall attenuation >3 dB and some very significant low frequency (250-1000 Hz) attenuation improvements;>4 dB. Thus, an opportunity exists to improve the attenuation resulting from the commercial production of viscoelastic foam earplugs. An increase of 3dB attenuation allows the user to double their exposure time in the sound field for which the hearing protector is rated. This Phase I project will be divided into three stages: 1. Verifying the results from the pilot samples. The results of our pilot experiments will be verified through collaboration with acoustic experts. The comparative attenuation of the samples will be measured using an impedance tube measurement system. 2. Characterizing and comparing the foam structures of these new foams and existing commercial foam earplugs. The foam structures will be measured using mercury intrusion porosimetry, x-ray micro CT scanning, and microscopy. 3. Optimizing the foam structure by comparing attenuation of varied 'controlled structure foams'. The structures of the new foams will be varied using known techniques and the resulting effects on attenuation will be measured.

Public Health Relevance:
Daily many tens of millions of Americans have their hearing exposed to potentially damaging noise. Foam earplugs are inexpensive, comfortable and widely used;however, they do not always provide enough protection, especially in high-noise industrial and military work environments or in low frequency noise. Success with this research to improve foam attenuation at all frequencies will result in a more effective foam earplug, reducing incidence of hearing loss - the most common industrial injury.

Thesaurus Terms:
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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.

Thesaurus Terms:
Acoustics;American;Area;Attenuated;Attenuation;Base;Businesses;Cell Size;Cell Wall;Cells;Cellular Structures;Collaborations;Commercial Application;Communication;Design;Devices;Drops;Drug Formulations;Ear Structure;Earplug;Electron Microscopy;Ensure;Environment;Evaluation;External Auditory Canal Structure;Field Survey;Filler;Foam Cells;Frequencies (Time Pattern);Gases;Goals;Government;Hearing;Hearing Impairment;Helicopter;Human Subject;Improved;Incidence;Industry;Industry Partner;Injury;Institutional Review Boards;Instrumentation;Laser Scanning Confocal Microscopy;Measurement;Measures;Mechanics;Meetings;Member;Mercury;Methods;Microscopy;Military Personnel;Music;Names;Noise;Occupational;Occupational Health;Optical Tomography;Performance;Persons;Phase;Physical Property;Principal Investigator;Property;Public Health Relevance;Research;Research Study;Response;Sampling;Seal;Sound;Structure;Success;Surfactant;Techniques;Technology;Testing;Time;Tool;Transportation;United States;Work;