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Sven Nordholm, Walter Kellermann,

Simon Doclo, Vesa Välimäki,

Shoji Makino, and John R. Hershey

[

from the

GUEST EDITORS

]

IEEE SIGNAL PROCESSING MAGAZINE [16] MARCH 2015

Signal Processing Techniques for Assisted Listening

atural hearing is a desirable

goal in many electronic

communication applica-

tions, such as hearing aids,

audio conferencing, gaming,

and virtual reality applications. The era of

low-power, high-complexity electronics

supports the implementation of computa-

tionally complex algorithms as needed to

provide a more natural listening environ-

ment for the advanced augmentation of

virtual reality and natural content.

As such, assisted listening techniques

provide the means to communicate audio

information from devices to human listen-

ers. The main objective is to provide the

user with a listening experience through

the device that resembles natural hearing

of the sound information. Prominent ap-

plications include virtual augmented au-

dio, hearing aids, and cochlear implants.

But the same techniques are also applica-

ble in other communication applications

such as monaural voice communication,

where additional spatial information can

greatly enhance the listening experience.

In the realm of hearing aids, current de-

vices aim to be more natural both for the

hearing impaired and profoundly deaf by

using new processing techniques. They

even promise to enhance the listening ex-

perience of so-called normal hearing us-

ers. Along with increasingly affordable and

growing computer power, a large variety

of elaborate algorithms for overlayed au-

dio or so-called augmented audio continu-

ously strive toward new applications in

gaming and telepresence to provide a “be-

ing there” experience.

The articles in this special issue of

IEEE Signal Processing Magazine (SPM)

focus on three main aspects of signal

processing in this domain: audio en-

hancement, presentation/rendering, and

evaluation. To limit the scope in this spe-

cial issue, machine-learning techniques

have been excluded. While it is under-

stood that future systems for assisted lis-

tening will greatly be influenced by

machine-learning-based algorithms, an-

other special issue dedicated to this de-

velopment can already be envisioned.

Audio signal enhancement, particular-

ly of speech signals, has a long research

tradition and still dominates the scene,

and, consequently, is also the main topic

of this special issue. Techniques for sin-

gle-channel and multichannel signal en-

hancement techniques play a preeminent

role in telecommunication, hearing aids,

and augmented headsets. Accordingly,

fundamental problems and state-of-the-

art techniques are presented in the article

“Multichannel Signal Enhancement Algo-

rithms for Assisted Listening Devices” by

Doclo et al. Beyond the description of the

generic algorithms, this article emphasiz-

es the specific problems and solutions for

hearing aids and headsets addressing both

the signal acquisition and the binaural

rendering aspect.

As a special technique for capturing and

describing the spatial information relevant

for assisted listening, multichannel tech-

niques that estimate the direct path infor-

mation and suppress a combination of

reverberation and diffuse noise are provid-

ed in the article “Parametric Spatial Sound

Processing” by Kowalczyk et al.

Two articles provide overviews on high-

ly relevant aspects of single-channel en-

hancement techniques: “Optimizing

Speech Intelligibility in a Noisy Environ-

ment” by Kleijn et al. focuses on techniques

for improving speech intelligibility using

perceptual criteria and auditory modeling,

and “Phase Processing for Single-Channel

Speech Enhancement” by Gerkmann et al.

provides a survey of techniques that utilize

both amplitude and phase information for

speech enhancement.

Processing and coding signals for cochle-

ar implants is addressed in the article “Sound

Coding in Cochlear Implants” by Wouters

et al. This article describes signal processing

techniques used in cochlear implants to

map the information extracted from an au-

dio signal onto cochlea excitation that a

profoundly deaf person can understand.

Rendering of audio aims at providing

an immersive, undisturbed listening expe-

rience for recorded information via loud-

speakers or headsets with typical applica-

tions demanding high-quality sound

reproduction, such as, e.g., home theaters,

gaming, or telepresence systems. Betlehem

et al. provide an overview of techniques to

deliver audio information to multiple lis-

teners via loudspeakers in their article

“Personal Sound Zones.” These techniques

also have applications in providing audio in

public areas without disturbing the sur-

roundings. Then the natural sound in the

environment is augmented by the rendered

audio. A similar concept to augment out-

side information using personal headsets is

presented by Välimäki et al. in “Assisted

Listening Using a Headset,” which also

Digital Object Identifier 10.1109/MSP.2014.2375972

Date of publication: 12 February 2015

THE MAIN OBJECTIVE

OF ASSISTED LISTENING

TECHNIQUES IS TO

PROVIDE THE USER

WITH A LISTENING

EXPERIENCE THROUGH

THE DEVICE THAT

RESEMBLES NATURAL

HEARING OF THE SOUND

INFORMATION.

THE WORLD’S NEWSSTAND

THE WORLD’S NEWSSTAND