Page 24 - Special Issue
P. 24

 Forensic Acoustics
Germanwings Flight 9525 that crashed in
of acoustical events, and educate the attorneys, defendants,
1958): “Current advances in the technology of electronics and sound recordings make inevitable their increased use to obtain and preserve evidence possessing genuine proba- tive value. Courts should deal with this class of evidence in a manner that will make available to litigants the benefits of this scientific development. Safeguards against fraud or other abuse are provided by judicial insistence that a proper foundation for such proof be laid.”
[...]“A review of the authorities leads to the conclusion that, before a sound recording is admitted into evidence, a foun-
the French Alps in March 2015. Forensic
judges, and juries about the meaning, significance, and limi-
acoustics comes into play also when there
tations of the recorded evidence (Audio Engineering Soci-
is a dispute about the likelihood that an
ety, 1996; Maher, 2009). Figure 2 depicts an interpretive an- acoustical product presents a hearing
notation that has been added to a time waveform to assist
hazard or interferes with the audibility of
with an investigation.
an aural emergency notification alarm. The domain of forensic acoustics even
Forensic Acoustics and the US Courts
includes forensic musicology for cases of
Audio forensics traces its origins to the development of por-
alleged copyright infringement of musi-
table recording equipment, and examples of the use of audio
cal style and intellectual property (Be-
gault et al., 2014). The impact of forensic
dation must be established by showing the following facts:
courts generally began to accept the unique importance of
musicology was evident in the recent suc-
(1) that the recording device was capable of taking the con-
tained via clandestine surveillance or wiretaps, there were
by entertainers Robin Thicke and Phar-
designated administrator) who are likely inexperienced with forensic audio interpretation.
ment’s protections against unreasonable searches and sei-
recording is authentic and correct; (4) that changes, addi-
tions or deletions have not been made in the recording; (5)
that the recording has been preserved in a manner that is
rell Williams to the heirs of the late singer
a sound software package. It depicts the amplitude vs. time waveform of approximately one
minute of audio recorded at an emergency dispatch center and includes utterances from the
audio recordings, especially in cases involving speech ob-
cessful litigation award of US$7.4 million land mobile radio systevmerasantdiothne nloocawl vofficeroefdthiendeisvpiadtechnecre. ;Fi(g2u)retshlaiktettheis oaplloewraetxoprerotfs
in damages a court ruled must be paid in forensic acoustics inform and educate attorneys and "triers of fact" (e.g., judge, jury,
significant considerations regarding the Fourth Amend-
zures and concern about the legal admissibility of a record-
the device was competent to operate the device; (3) that the
 Marvin Gaye.
ing as being a bona fide representation of the sonic events
interpretation of tangible audio recordings, forensic acous-
Despite its occasional high profile, forensic science has come
shown to the court; (6) that the speakers are identified; and
actually present during the recording process.
tics may also treat questions of audibility in the context of
up against some serious scrutiny and soul searching in re-
(7) that the conversation elicited was made voluntarily and
The McKeever Case
litigation or criminal prosecution, such as civil annoyance
cent years, including an influential 2009 report from the
in good faith, without any kind of inducement.”
Among the key cases in the US federal court system regard-
complaints from an outdoor performance venue, noise lev-
US National Research Council that criticized many forensic
Since the early 1960s, US Federal Bureau of Investigation
ing the admissibility of audio forensic evidence is United
els produced by takeoffs and landings at an airport that vio-
fields, including audio forensics, for lacking scientific evalu-
(FBI) laboratories have developed techniques and proce-
States v. McKeever (1958). In the McKeever case, two de-
late local statutes, or whether or not a scream or other sound
ation of reliability and error rates (National Academy of Sci-
dures for assessing the authenticity and audible contents of
fendants were indicted for extortion in an antiracketeering
was likely to have been detectable under the circumstances
ences, 2009). Thus, it is increasingly important that the sci-
forensic audio recordings obtained from law enforcement
prosecution involving the International Longshoremen’s
claimed by an ear witness.
ence in forensic investigations be based on unquestionably
investigations, and similar capability has been instituted
Association. After his indictment, the defendant McKeev-
objective interpretation and not merely subjective opinions,
Forensic acoustics experts who deal with recorded evidence
er had arranged to make a surreptitious tape recording of
in other public and private forensic acoustics labs around
as has sometimes been the case.
are most often consulted about three concerns: authenticity,
a conversation he had with an individual who later was a
the world (Koenig, 1990). As described in Modern Audio enhancement, and interpretation (Maher, 2010).
I begin with a description of several key elements, terms, and
Forensics: Digital “Good” and Digital “Bad,” tenet 3, au-
witness in the trial. During the trial, McKeever’s defense
historical origins of forensic acoustics, primarily in terms of
tAhuetnhteicnitiycidtyetdeermnoitneastitohne,ahcacsepbteacnocme oefmaorreecodridffiincgulatsinbeoinugr
eurnaaoltfereadda/nwdritreudeitgoitiatlsrseocuorcdeinagndancdhacionmopf uctuesrtopdroy.cCesrsiimng-
cinoaml paanrdedciwvitlhctahseshmistaoyrihcirneglieanocne aondpishpyustiecalbaonuatlotghemcaigr-
ncuetmicstanpcees.s under which a recording was made and whether
team sought to challenge under cross-examination the wit-
the judicial system in the United States. Next, I consider the
ness’ testimony by playing a portion of the clandestine tape
challenge of determining authenticity in the age of digital
recording to refresh the witness’ recollection. The court al-
data storage and the corresponding opportunities present-
lowed the tape to be played but only via headphones so that
ed by the increasingly wide deployment of audio recording
audible material in the recording could have been deleted,
the witness could hear it but not the jury. When the defense
Forensic Acoustics and Watergate
apparatus in memo recorders, digital cameras, and virtu-
added, or otherwise edited after the fact (Koenig 1990; Au-
then sought to have the recording played in court so that
A significant turning point in the practice of forensic acous-
ally every contemporary smartphone. Finally, I sum up the
dio Engineering Society, 2000).
the jury also could hear it, the prosecution objected to the
tics in the United States occurred 15 years after McKeever
field by mentioning areas in which interested members of
use of the tape because its admissibility as evidence had not
Enhancement involves signal-processing techniques that at-
the Acoustical Society of America (ASA) can get involved to
during the Watergate scandal. In 1971, late in his first term
been established. Specifically, the court had to address the
tempt to improve the intelligibility of speech, the clarity of
provide new and innovative research that will help advance
in office, President Richard Nixon directed the Secret Ser-
fact that the recording was obtained secretly out of court, the
specific background sounds, or the overall signal-to-noise ra-
forensic acoustics.
vice to install audiotaping systems in the Oval Office and
participants were not sworn, the witnesses disputed whether or not they recognized even their own voices, and the legal
tio of the recording. Modern enhancement techniques use a
What Is Forensic Acoustics?
private office in the Executive Office Building (EOB) next
chain of custody had not been demonstrated to ensure ad-
nal recording medium is used only to obtain the work copy for
Forensic acoustics, or audio forensics, is the specialty field
to the White House, and at Camp David, the president’s re-
missibility of the audio evidence.
enhancement (Musialik and Hatje, 2005; Koenig et al., 2007).
of acoustics and audio engineering that deals with the ac-
treat in rural Maryland. The existence of these recording systems was known only to a select group of individuals
The court examined these questions and considered a num-
Finally, interpretation refers to the description of the acous-
quisition, analysis, and evaluation of audio recordings that
and to the Secret Service (Nixon Presidential Library and
ber of prior federal court rulings, then established what the
tical evidence in words, pictures, statistics, and graphs that
are to be presented as evidence in an official inquiry or in a
Museum, 2015). President Nixon presumably assumed that
forensic acoustics community now refers to as the Seven
help address investigative questions, explain the sequence
court of law (Maher, 2009). In addition to the analysis and
the recording system's existence would be of interest to no
Tenets of Audio Authenticity (United States v. McKeever,
Summer 2015 | Acoustics Today | 23
24 | Acoustics Today | Spring 2020, Special Issue
24 | Acoustics Today | Summer 2015 Reprinted from volume 11, issue 3
the Cabinet Room of the White House, in the president’s
high-quality digital copy of the original recording so the origi-
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