International Journal of Innovative
Computing, Information and Control
Volume 6, Number 3(B), March 2010

ICIC International c 2010 ISSN 1349-4198
pp. 1389–1400

AUDIO DATA HIDING THAT IS ROBUST WITH RESPECT TO
AERIAL TRANSMISSION AND SPEECH CODECS
Akira Nishimura
Department of Media and Cultural Studies
Tokyo University of Information Sciences
4-1 Onaridai, Wakaba-ku, Chiba 265-8501, Japanakira@rsch.tuis.ac.jp

Received December 2008; revised May 2009
Abstract. A technique for audio data hiding by using subband amplitude modulation
was evaluated by computer simulations in terms of robustness with respect to the cumulative eﬀects of reverberations, background noise, and encoding and decoding with a speech
codec. Speech signals from 22 speakers and signals from 100 pieces of music were used as
the host audio data. Computer simulations revealed that speech and music signals withbackground noise and reverberations were able to transmit at least 80% of the embedded
data at 8 bps after encoding and decoding using the Adaptive Multi-Rate (AMR) speech
codec at a bitrate of 12.2 kbps. In actual measurements in a reverberant room using acell phone terminal, data hidden in a 12.2-kbps AMR recording having a signal-to-noise
ratio of 20 dB was detected at a mean bit error rate of 15 %. The sound quality degradation induced by data hiding was objectively measured using the perceptual evaluationof speech quality (PESQ) and perceptual evaluation of audio quality (PEAQ) algorithms.
The average PESQ score of the speech signals approximately corresponded to a subjective
evaluation of ‘fair’, while the average PEAQ score of the music signals corresponded toa somewhat lower subjective evaluation of ‘slightly annoying’.
Keywords: Acoustic application, Speech codec, Acoustic noise, Telephony, Information
system, Microphone

1. Introduction. Watermarking technologies are expected to be applied to copyright
management, tamper detection and recovery [1] of multimedia data, including images [2]and video [3]. Audio watermarking techniques are usually associated with content protection and digital rights management of music. Another application of audio watermarks is
the inclusion of augmentation data [4]. For example, if an announcement broadcast fromloudspeakers in a public area contains embedded text, the embedded data can potentiallybe extracted in real time from the speech signal upon detection by a microphone. Such an
application would be invaluable for hearing-impaired people. The signal can be received
by a portable device, such as a PDA or a cellular phone. Such an application requires
a method of audio data hiding that is robust with respect to reverberations, reflections,and background noise [5].
If a cellular phone is used as a terminal for displaying information, extracting datausing the phone would necessitate the installation of additional decoding software thatwould require excessive processing power. To solve this problem, sounds received by acellular phone can be transmitted via a cellular network to a server computer for data
extraction. The information extracted by the server computer can be transmitted to thecellular phone terminal via e-mail. In this situation, the embedded data should be robust
against the speech codecs employed in the cellular network.
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