Psychoacoustics: A Brief Historical Overview William A. Yost From Pythagoras to Helmholtz to Fletcher to Green and Swets, a centu- ries-long historical overview of psychoacoustics. Postal: Speech and Hearing Science 1 Arizona State University What is psychoacoustics? Psychoacous- PO Box 870102 tics is the psychophysical study of acous- Tempe, Arizona 85287 tics. OK, psychophysics is the study of USA the relationship between sensory per- ception (psychology) and physical vari- Email: ables (physics), e.g., how does perceived [email protected] loudness (perception) relate to sound pressure level (physical variable)? “Psy- chophysics” was coined by Gustav Fech- ner (Figure 1) in his book Elemente der Psychophysik (1860; Elements of Psycho- physics).2 Fechner’s treatise covered at least three topics: psychophysical meth- ods, psychophysical relationships, and panpsychism (the notion that the mind is a universal aspect of all things and, as Figure 1. Gustav Fechner (1801-1887), “Father of Psychophysics.” such, panpsychism rejects the Cartesian dualism of mind and body). Today psychoacoustics is usually broadly described as auditory perception or just hearing, although the latter term also includes the biological aspects of hearing (physiological acoustics). Psychoacoustics includes research involving humans and nonhuman animals, but this review just covers human psychoacoustics. With- in the Acoustical Society of America (ASA), the largest Technical Committee is Physiological and Psychological Acoustics (P&P), and Psychological Acoustics is psychoacoustics. 1 Trying to summarize the history of psychoacoustics in about 5,000 words is a challenge. I had to make difficult decisions about what to cover and omit. My history stops around 1990. I do not cover in any depth speech, music, animal bioacoustics, physiological acoustics, and architectural acoustic topics because these may be future Acoustics Today historical overviews. I focus on aspects of pitch perception and sound source localization because these topics have a very long history of study. I briefly cover other topics, but many had to be omitted. The overview will be “English-centric,” at least after the 1920s. I am fluent only in English, so my knowledge of psychoacoustics is dominated by what I have heard and read, and Acoustics Today is a magazine of the ASA and JASA is the scientific journal of the ASA. I believe it is fair to say that the majority of the articles written on psychoacoustics from 1929 (ASA’s founding) to the end of the 20th century appeared in English in JASA. I have attempted to recognize key scholars who did not always publish in English, but I am sure that I have not done a good job of covering non-English psychoacoustic contributions. 2 See Internet Archive BookReader: https://www.google.com/#q=Elemente+der+Psychophysik+. 46 | Acoustics Today | Summer 2015, volume 11, issue 3 ©2015 Acoustical Society of America. All rights reserved. Table 1: ASA Psychoacoustician Award Winners and Presidents Helmholtz-Rayleigh Gold Medal Silver Medal ASA Presidents Interdisciplinary Silver Harvey Fletcher 1957 Lloyd A. Jeffress 1977 W. Dixon Ward 1991 Harvey C. Fletcher 1929 Ira J. Hirsh 1992 Eberhard Zwicker 1987 Jens P. Blauert 1999 J. C. R. Licklider 1958 David M. Green 1994 David M. Green 1990 William M. Ira J. Hirsh 1967 Brian C. J. Moore 2014 Nathaniel I. Hartmann 2001 Karl D. Kryter 1972 Durlach 1994 David M. Green 1981 Neal F. W. Dixon Ward 1988 Viemeister 2001 William M. Brian C. J. Moore 2002 Hartmann 2001 H. Steven William A. Yost 2005 Colburn 2004 Judy R. Dubno 2014 William A. Yost 2006 Although a defining aspect of Fechner’s psychophysics was a sound was produced when the card vibrated. The pitch of relating perception to physics, attempts to find the physical the sound rose as the wheel’s rotational speed increased. A bases for perception predate Fechner by centuries. The early century and a half later, Felix Savart (1791-1841) refined the Greeks, such as Pythagoras, sought physical/mathematical wheel to study human hearing (Figure 2).3 explanations for many aspects of music. The Greeks did not By the 18th century, the have a name (e.g., psychoacoustics) for their studies, but main method for creat- they were engaged in psychoacoustics just as much as Fech- ing sound for the study of ner and others before and after him. pitch was the tuning fork, I divide the history of psychoacoustics into several peri- invented by John Shore in ods: Psychoacoustics Before the 19th Century, the Realm 1711. Shore (1662-1752) of Helmholtz, Bell Laboratories, the Theory of Signal De- was an accomplished trum- tection, the Study of Complex Sound, and Auditory Scene Figure 2. An illustration of a peter and lutenist, and he Savart wheel. An earlier ver- Analysis (Yost, 2014; Table 1). I have relied on the classic sion was used by Hooke to study is reported to have said at perception history text by E. G. Boring (1942) and R. B. sound frequency and pitch. the beginning of a con- Lindsay’s article on the history of acoustics (1966). cert that he did not have a pitch “pipe,” a common means to tune instruments, but he Psychoacoustics Before did possess a pitch “fork.” Other forms of resonators, sirens, the 19th Century tubes, and strings were used to study sound until the use As already mentioned, Pythagoras and fellow scholars were of electrical devices and the vacuum tube (invented about fascinated by music. Greek musical instruments were sim- 1910) came into existence. ple-stringed (e.g., lyre), tubed (e.g., flute), and percussion The early scholars had their humorous observations as well. (e.g., tympanum) instruments. Greek scholars tried to un- For example, Leonardo Da Vinci wrote “an average human derstand the physical/mathematical bases of musical scales, looks without seeing, listens without hearing, touches with- consonance, and dissonance produced by these instruments. out feeling, eats without tasting, moves without physical Aristotle (around 350 BC) was the first to suggest that sound awareness, inhales without awareness of odor or fragrance, is carried by air movement. But Leonardo De Vinci (around and talks without thinking.” 1500) was likely the first to realize that such movement was probably in the form of waves. Galileo Galilei, 100 years lat- Realm of Helmholtz er, scraped a chisel across a brass plate, producing a screechy (1800s-Early 1900s) pitch. Galileo calculated that the spacing of the grooves Hermann von Helmholtz was a commanding, if not the lead- caused by the chisel was related to the perceived pitch of ing, scientist of the 19th century. His book (1863/1954) On the screech. However, it wasn’t until the 17th century that the Sensations of Tone as a Physiological Basis for the Theory the relationship between vibratory frequency and pitch was of Music was the major reference for hearing and musical confirmed. Robert Hooke (1635-1703) made a wheel with small teeth sticking out from the edge at equal intervals. As 3 Wave-Action in Nature. (1873).The Popular Science Monthly, the wheel rotated on an axle and the teeth pressed on a card, Volume III, 7–8. Summer 2015 | Acoustics Today | 47 HIstory of Psychoacoustics perception for many de- perceived pitch. However, Seebeck’s siren was constructed cades (Figure 3). With the so that the fundamental frequency was not physically pres- publication of Fechner’s ent, only the harmonics. The pitch of this “missing funda- and Helmholtz’s books, the mental” sound appeared to be the same as when the funda- study of hearing turned mental was present. This implied that the fundamental of a from one of observations harmonic sound does not have to be physically present for based on a scientist’s per- the pitch to be perceived as that of the fundamental. This ceptions to a more system- was at odds with Ohm’s acoustic law as interpreted by Helm- atic collection of psychop holtz. Helmholtz cited several reasons why Seebeck’s missing physical data, often stated fundamental pitch was an “artifact,” and it was many years in terms of acoustical vari- before the missing fundamental stimulus was cited as a se- ables, in somewhat well- rious challenge to Helmholtz’s spectral/resonance theory of controlled experiments. pitch perception. Decades later, Schouten (1940) formulated his “residue theory,” which suggested that the missing fun- Figure 3. Hermann von Helm- Many studies of hearing damental pitch was based on the temporal amplitude enve- holtz (1821-1894) and his book occurred in the 18th cen- lope of the missing fundamental stimulus that would exist in On the Sensation of Tones. tury, and two areas of inter- a high-frequency region after the sound was transformed by est, pitch and sound source inner ear filtering processes. Helmholtz’s spectral approach localization, have had a lasting impact on psychoacoustics. to explaining pitch perception and Schouten’s temporal ap- Helmholtz was influenced by Georg Simon Ohm’s (1789- proach characterize today’s debate as to the probable audito- 1854) “acoustic law” that stated that the ear performs a lim- ry mechanisms accounting for pitch perception (Yost, 2009). ited Fourier analysis by determining the sinusoidal compo- nents of complex sound. Ohm is perhaps better known for Perceptual scientists in the 19th century observed that the his work on electricity and for whom the unit of resistance source of a sound could be spatially located based entirely is named. Fourier (1768-1830), a French physicist/math- on sound despite the fact that sound has no spatial proper- ematician working earlier in the 19th century, established a ties. So how could sound provide information about spatial theorem regarding complex fluctuations of heat over time. location? Lord Rayleigh (James William Strutt, 3rd Baron Fourier’s theorem can be applied to sound pressure varying Rayleigh, 1842-1919, Nobel Prize in Physics 1904) and oth- as a function of time.