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Digital Object Identifier 10.1109/MSP.2014.2369191

Date of publication: 12 February 2015

istorically, headphones have mainly been used for

analytic listening in music production and in

homes. During the last decade, with the boom of

dedicated music players and mobile phones, the

everyday use of light headphones has become highly

popular. Current headphones are also paving the way for more

sophisticated assisted listening devices. Today, active noise con-

trol (ANC), equalization techniques, and a hear-through function

are already a standard part of many headphones that people com-

monly use while traveling. It is not difficult to predict that, in the

near future, a headset will be a “hearing aid for those with normal

hearing,” which can improve listening conditions for example in

a noisy environment.

Additionally, mobile augmented reality has become a hot topic

[1], and new products such as the Google Glass will make it more

common. On the audio side of augmented reality systems, mixing

of the ambient and reproduced sounds will be an essential fea-

ture. Augmented reality headsets may also serve as the main user

interface for the disappearing computer in the future, when

visual displays and tangible keyboards vanish.

This article gives an overview of various signal processing

techniques needed in assisted listening. The basic use case and

various others are described in Figure 1, which shows how head-

phone listening can be extended by incorporating external micro-

phones and some signal processing. Assisted listening in heavy

background noise environments, such as in an airplane, can be

implemented using ANC [2].

HEADPHONE LISTENING IN A NOISY ENVIRONMENT

When headphones are used in a noisy environment, their design

goals are somewhat different than those of a conventional pair of

high-fidelity (hi-fi) headphones. The most important feature of

mobile headphones is the noise isolation capability, which can be

passive or enhanced with ANC. Furthermore, the headphone fre-

quency response can be designed to manage noisy environments,

typically by boosting the bass end of the response, as natural

ambient sounds have most of their energy at low frequencies

(such as bus or airplane noise) and headphones usually attenuate

low frequencies the least.

EARPHONES—IMAGE LICENSED BY INGRAM PUBLISHING

[

Vesa Välimäki, Andreas Franck, Jussi Rämö, Hannes Gamper, and Lauri Savioja

]

[

Enhancing audio perception in real,

augmented, and virtual environments

]

Assisted Listening

Using a Headset

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