The Fusion and Layering of Noise and Tone: Implications for Timbre in African Instruments Author(s): Cornelia Fales and Stephen McAdams Source: Leonardo Music Journal, Vol. 4 (1994), pp. 69-77 Published by: The MIT Press Stable URL: http://www.jstor.org/stable/1513183 Accessed: 03/06/2010 10:44 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.jstor.org/action/showPublisher?publisherCode=mitpress. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The MIT Press is collaborating with JSTOR to digitize, preserve and extend access to Leonardo Music Journal. http://www.jstor.org 4 A B S T R A C T SOUNDING THE MIND Since their earliest explora- The Fusion and Layering of Noise tions of Africanmusic, Western re- searchers have noted a fascination on the part of traditionalmusicians and Tone: Implicatons for Timbre for noise as a timbralelement. The authors present the results of per- ceptual and acoustic investigations in African Instruments of the fusion and "layeringnof noise and tone. These results have implicationsfor pitch and timbre in both traditionaland non-traditional, acoustic and synthesized music. CorneliaFales The results define possible percep- tual relations between noise and and StephenMcAdams tone and reveal that the construc- tion of noise devices should follow relativelyprecise acoustic rules in- volving the frequency, the band- width and the level of the noise relative to those of the tone. The results also exemplify the fusion of From theirfirst contact with African music, West- wardestablishing the parameters twoextremely different timbres, ern ethnomusicologistshave remarked on the predilectionof of noise and tone that influence withimplications for the blendingof the perceptual relation between instrumentaltimbres in an orches- Africanmusicians to "layer"(or superimpose) musical and tralsethng. The expenments non-musicalsound until the distinctionbetween them is lost them. We consldered three pos- shouldbe of interesttocomposers [1]. In particular,it has been observed that African music sible relationsbetween noise and whosynthesize mixtures of noise showsa special fascinationwith 'Cnoise''-thetransformation tone: (1) fusion (the noise and andperiodicsoundandforwhom of ordinary,mundane sounds into the substance of music. tone are perceptuallyintegrated the controlof suchmixtures rb mains problemabc. And while the manufactureof classicalinstruments and the lnto a slngle sound event, both performancepractice of Westernmusicians has aimed toward contributing to the perceptual reducingthe amountof extraneousnoise producedby an in- qualityof the event), (2) laymng strument,African musicians augment the naturalnoise po- (the two components are perceptuallysegregated into dis- tential of their instrumentby attachingnoise-makers such as iinct percepts,each with its own perceptualqualities) and (3) rattling seeds or bottle caps on which the vibrationsof the maskingoftone by noise (the more intense noise "coversup" main resonatoroperate. The effect is a complicatedlayering the tone that can thus no longer be heard andhas no percep- of sound, rich in aperiodiccomplexity. tual effect on the noise component). Layering is distin- One of the motivationsfor our study was the realization guished from fusion and maskingin that a layeredtone can that the combination of noise and musical elements, tradi- be heard separatelyfrom the noise. Whilea tone that is fused tionallydescribed by ethnomusicologistsas "layering,"actu- with a noise cannot be heard separately,it still contributesto ally takes at least two perceptualforms. Either the sound is the timbralquality of the noise; a masked tone has no such trulylayered, and listenershear twoor more perceptuallydiF effect, because it has been perceptually"eradicated." These tinct sounds concurrently,or the physicallysuperimposed three perceptualphenomena appear to depend on variations sounds are perceptuallyfused, so that listenershear a single of three acousticparameters: (1) the relativeintensity levels sound a blend of the two sounds neither of which is iden- of the two components, (2) the bandwidthof the noise and tifiable as the primar-yor the superimposedsound. A more (3) the center frequency of the noise band relative to the commonlyrecognized example of this distinction is the dif- tone frequency.Since informalpilot tests showedthat, in ad- ference betweena voice speakingthrough or in the presence dition to these parameters,the perceptualrelation between of noise (layerednoise and voice) and a hoarse voice speak- ing (noisyvoice). The directionof our researchhas involvedboth perceptual Fig. 1. Intensity series: Means (filled circles) and standard devia- experimentand acousticanalyses. Like manypsychoacoustic tions (SD) (vertical bars indicate i 1 SD) of responses for each in- studies, the first (experimental)part of our investigationin- tensity difference between tone and noise for high register stimuli volved the use of artificialstimuli, reduced to controllable with a 100-Hz band of noise centered on a 400-Hz tone. acoustic variables. To complement this part, an acoustic INTENSllY SERIES,high register analysisof real African instruments in which noise plays a prominent part was essential to verify the relevance of our 6- experimental results to sounds actuallyproduced by those 'e instruments.In particular,our experimentswere geared to- g: V) 3 Cornelia Fales (ethnomusicologist), Institut de Recherche et Coordination Acoustique/Musique (IRCAM), 1 place Stravinsky, F-75004 Paris, France. 2 Stephen McAdams (experimental psychologist), Laboratoire de Psychologie Experimentale (CNRS), Universite Rene Descartes, EPHE, 28 rue Serpente, F-75006 Paris, France. Manuscript solicited by Kathryn Vaughn. -2s -1s -s s 1S 25 Received 11 May l994. Difference in noise and tone level (dB) LEONARDO MUSIC JOURNAL, Vol. 4, pp. 69-77, 1994 K)1995 ISAST 69 - -t | g INTENSll Y SERIES,low register North Americans.Since the aim of this . part of the work was to establish some Fig. 2. Intensity se- basic psychoacousticthresholds and be- 6" " * _ ' ries: Means (filled cause psychoacousticphenomena at this circles) and stan- level are generallythought to be a func- dard deviations tion of the human hearing apparatus (SD) (vertical bars (whichis essentiallythe same for all hu- * indicate + 1 SD) of 3 tC * responses for each man beings), we considered the results intensity difference obtained from this study to reflect uni- between tone and versal properties of auditory percep- noise for low regis tion althoughthis assumptionwarrants 1 ter stimuli with a verificationin future research.From an , 100-Hz band of , . ethnomusicologicalpoint of view, how- -25 -15 -5 5 15 25 noise centered on a ever,it is noteworthythat informalpilot Differenceinnoise and tone 1e Level (dB) l,OOO-Hztone. testswith these subjectsrevealed that the notion of fusion between dissimilartim- breswas a difficultconcept to graspintel- noise and tone was greatly affected by -in which the noise center fre- lectuallyand, even more so, perceptually. the pitch register of the two elements, cywas tested relative to the tone Initially,subjects were askedto rate on a each of the three parameterswere var- Lency-the tone varied as described continuum the "degreeof fusion"dem- ied for stimuliconstructed around both in high and low registers, and the onstratedby a seriesof stimuli,but it be- high and low registers (centered at r frequency of the noise was offset came evident that the subjectswere un- 1,000 Hz and 400 Hz, respectively). the tone by up to 200 Hz in the low clear as to the definition of the terand up to 400 for the high reg- perceptualphenomenon that they were The noise in this last series had a askedto judge. Therefore,as an alterna- PERCEPrUAL RESEARCH bandwidth of 100 Hz. tive, the subjectswere askedwhether the General Meffiod Wa given trial in one of the series, a acoustic components comprisedone or The experiments were organized in /noise stimulus was presented two sounds,since fusion transformsmul- three series, each testing the effect of a times in succession. Each stimulus tiple elements into a single unitaryper- different acoustic parameteron tone/ 00msec in duration and the onsets cept. Subjects were asked, in other noise fusion. In the Intensity Series, ffsets of the noise and tone compo- words, to rate the degree to which the pure tones (sinusoidal waveform) in ,were synchronous. The tone was tone could be heard separatelyfrom the high and low registers were combined nted at a mean level of 57 dB SPL noise in each trial. with band-filteredwhite noise having a ingrandomly by +