Numerical modelling of supra-aural headphones

Kelly, L

Abstract

Headphone design is facilitated by modelling and has traditionally been carried out
using lumped parameters, which are efficient but limited to low frequencies. In this
investigation a wave based approach is taken using finite elements to introduce a
headphone modelling tool which has the capability to predict high frequency
harmonic components in the acoustic field. The development of these increased
bandwidth headphone modelling capabilities is carried out over 3 discrete design
phases involving 2D axisymmetric and 3D models with the key components being
the porous cushion, the headphone driver and the geometric profile of the pinna.
The cushion is represented using a well established 6 parameter porous material
model as an equivalent fluid which is a convenient approach for a finite element
implementation. Characterisation of porous materials using such an approach
generally involves an expensive and time consuming measurement regime; this
investigation has shown that multi-dimensional optimisation gives an adequate
representation without need for this. Simulations using the finite element model
headphone model are compared against measurements taken on a HATS
mannequin and show good agreement up to 10 kHz, a significant improvement in
bandwidth over previous publications. An investigative survey was carried out
using these software tools of various headphone dimensional parameters, including
a representation of pinna variation which, significantly, shows wide variations in
frequency responses at high frequency. If used as an indication of inter-subject
variation it suggests the ability to model accurately to a high frequency may only
have limited benefits for headphones intended for many different wearers.

Citation

Kelly, L. Numerical modelling of supra-aural headphones. (Thesis). Salford : University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 3, 2012
• Award Date: Jan 1, 2010