Tampere, Finland, and Buxton, Maine
oSummary: HearFones (HF) have been designed to enhance auditory feedback
during phonation. This study investigated the effects of HF (1) on sound
perceivable by the subject, (2) on voice quality in reading and singing, and (3)
on voice production in speech and singing at the same pitch and sound level.
Test 1: Text reading was recorded with two identical microphones in the
ears of a subject. One ear was covered with HF, and the other was free. Four
subjects attended this test. Tests 2 and 3: A reading sample was recorded from
13 subjects and a song from 12 subjects without and with HF on. Test 4: Six
females repeated [pa:p:a] in speaking and singing modes without and with
HF on same pitch and sound level.
Long-term average spectra were made (Tests 1–3), and formant frequencies,
fundamental frequency, and sound level were measured (Tests 2 and 3). Sub-
glottic pressure was estimated from oral pressure in [p], and simultaneously
electroglottography (EGG) was registered during voicing on [a:] (Test 4). Voice
quality in speech and singing was evaluated by three professional voice trainers
(Tests 2–4).
HF seemed to enhance sound perceivable at the whole range studied (0–8
kHz), with the greatest enhancement (up to ca 25 dB) being at 1–3 kHz and
at 4–7 kHz. The subjects tended to decrease loudness with HF (when sound level
was not being monitored). In more than half of the cases, voice quality was
evaluated “less strained” and “better controlled” with HF. When pitch and
loudness were constant, no clear differences were heard but closed quotient
of the EGG signal was higher and the signal more skewed, suggesting a better
glottal closure and/or diminished activity of the thyroarytenoid muscle.
Key Words: Auditory self-monitoring—Voice training.
Accepted for publication May 5, 2003.
Based on a presentation given at the Voice Foundation’s 31st
Symposium “Care of the Professional Voice,” Philadelphia, PA,
June 2002.
From the *Department of Speech Communication and Voice
Research, University of Tampere, Tampere, Finland; †NEXTEP
Incorporated, Buxton, Maine, U.S.A.; **Department of Acting,
University of Tampere, Tampere, Finland; ††Phoniatric Depart-
ment, Tampere University Hospital, Tampere, Finland.
Address correspondence and reprint requests to Anne-Maria
Laukkanen, Department of Speech Communication and Voice
Research, FIN-33014 University of Tampere, Tampere, Finland.
E-mail: Anne-Maria.Laukkanen@uta.fi
Journal of Voice, Vol. 18, No. 4, pp. 475–487
0892-1997/$30.00

2004 The Voice Foundation
doi:10.1016/j.jvoice.2003.05.007Effects of HearFones on
Voice Q
¨
*Anne-Maria Laukkanen, †Nils P
**Tiina Syrja, **Arla Sal47Speaking and Singing
uality
eter Mickelson, *Marja Laitala,
, and ††Marketta Sihvo5

ANNE-MARIA LAUKKANEN ET AL476INTRODUCTION
Auditory self-monitoring is traditionally regarded
as highly important in voice and speech training.
The importance of auditory feedback in the control
of phonatory quality can be observed clearly, for
example, in the case of the deaf. Deviant voice qual-
ity is a common characteristic among speakers with
severe hearing impairment.1–3
One problem related to the normal use of auditory
self-monitoring in voice training is the fact that we
do not hear ourselves in the same way as other
people do. We tend to hear our own voices darker be-
cause the lower partials of our voices travel better
around and through the head to the ear (about the
differences between air-conducted and bone-con-
ducted sound, see, e.g., Howell4 and Po¨rschmann5),
and the higher partials tend to be transmitted more
directionally from the mouth forward. This also
makes it more difficult for us to hear the possible
breathiness (turbulence in high-frequency range)
and acoustic detail in our voices.
In voice training tradition, various tricks have
been used to give the trainee a better idea of how
he/she sounds to the audience. The trainee may be
instructed to phonate against a wall,6 or he/she is
instructed to cup a hand to the ear and/or to cross the
arms in front of the face to improve sound reflection
back to the ear.7
A commercial product, HearFones (NEXTEP,
Buxton, Me) (HF), has been developed to serve more
comfortably the same purpose as these traditional
tricks and thus to act as a learning tool (see Figure
1). Mounting over the head in the same manner
as conventional headphones, HF use ellipsoidal
acoustic reflectors, with one focus at the mouth and
the other at the ear, carrying sound normally di-
rected to the audience into the user’s own ears. The
intent of the reflectors is to provide equal-length
sound paths to avoid phase distortion. Developed
originally for choral singers, HF permit free
hearing of ambient sounds and free voice production
to the audience. HF are described in U.S. Patent
6,229,901.
The present preliminary study aims to answer the
following questions:
(1) How do the HF affect the sound perceived
by the subject him/herself during phonation?Journal of Voice, Vol. 18, No. 4, 2004FIGURE 1. HearFones with ellipsoidal reflectors and acousti-
cally open foam earpads.
(2) How do the HF affect voice quality in text
reading?
(3) How do the HF affect voice quality in
singing?
(4) Do the HF affect voice production in speech
and singing if fundamental frequency and
sound level are kept constant?
MATERIALS AND METHODS
Recordings
Test 1. Effects of HF on perception
In order to study the effects of HF on the sound
perceivable to the subject of his/her voice during
phonation, a text reading sample (91 words, ca 30
seconds) was recorded simultaneously with two iden-
tical omnidirectional tiepin microphones (TCM110,
frequency response 50–18,000 Hz, sensitivity
52