title: Acoustic Performance of 3D Printed Nanocomposite Earmuff.
abstract: BACKGROUND
  Hearing protection devices are one of the primary noise reduction tools in developing countries. This study is intended to produce and apply acrylonitrile butadiene styrene (ABS)/clay nanocomposites to fabricate a laboratory single cup earmuffs and then compare it with double cup and single cup pure ABS earmuffs in terms of noise attenuation performance and comfort. In addition, the noise attenuation performance of single cup pure ABS earmuffs is compared with double cup pure ABS earmuffs.
  
  
  METHODS
  ABS/nanoclay filament was fabricated using a twin screw extruder. A three dimensional (3D) printing machine and a 3D model of earcup, designed by solid work software, were applied to print single and double cup earmuffs using ABS/nanoclay composite and pure ABS filaments. Finally, using an acoustic test fixture, objective noise attenuation test was performed on three different types of earmuffs, including with and without nano material and a secondary cup. Moreover, earmuffs weight was measured as a comfort component.
  
  
  RESULTS
  Insertion loss and calculated noise reduction rating (NRR) of single cup ABS/nanoclay earmuffs (NRR=19.4 dB) and double cup pure ABS earmuffs (NRR=18.93 dB) were improved in comparison with single cup pure ABS earmuffs (NRR=15.7 dB). Additionally, both single cup earmuffs were significantly lighter than double cup earmuffs. Although single cup nano and double cup earmuffs had nearly the same attenuation performance, single cup nano earmuffs were 74 gr lighter than double cup earmuffs, so with reference to comfort, single cup nano earmuffs will probably be more acceptable.
  
  
  CONCLUSIONS
  From this survey it might be concluded that, even though single cup ABS/nanoclay earmuffs was lighter than double cup pure ABS earmuffs, it had approximately more attenuation performance in comparison with double cup pure ABS earmuffs. Consequently, users are probably more prone to wear light- weight single cup ABS/nanoclay earmuffs as a result of improved comfort. In short, ABS/nanoclay composite can be considered a good choice in products with the necessity of high acoustic performance and low weight.
authors.affiliation: Tehran university of medical science. saeidahmad@gmail.com.
authors.forename: Saeid
authors.initials: S
authors.lastname: Ahmadi
authors.forename: Parvin
authors.initials: P
authors.lastname: Nassiri
authors.forename: Ismaeil
authors.initials: I
authors.lastname: Ghasemi
authors.forename: Mohammad R
authors.initials: MR
authors.lastname: Monazzam Ep
mesh_terms: D000162:Acoustics; D004430:Ear Protective Devices / Q000592:standards*; D004867:Equipment Design; D006317:Hearing Loss, Noise-Induced / Q000517:prevention & control*; D006801:Humans; D008144:Loudness Perception; D053761:Nanocomposites / Q000737:chemistry*; D009622:Noise / Q000009:adverse effects*; D066330:Printing, Three-Dimensional; D018570:Risk Assessment