Applying the Benefits of Unamplified Acoustic Music to Performances with Amplification

Transcription

1 Applying the Benefits of Unamplified Acoustic Music to Performances with Amplification Kenneth D. Jacob Chief Engineer, Bose Professional Systems Division Director, Live Music Technology Group January, 2004

2 M u s i c i s H u m a n From both an anthropological and neurological perspective, it appears that music is a fundamental part of being human. For example, no present-day culture exists without music as one of its central activities. 1 And recent archeological discoveries show that music has been a part of human existence for an extraordinarily long time. 2, 3 Neuroscientists have found that powerful musical experiences excite the same part of the brain associated with activities related to reproduction and survival. 4 Thus music, like language, appears to be inseparable from what it means to be human. Numerous musical innovations have occurred over the millennia: musical instruments were invented and refined, new musical styles were created, and acoustically tuned performance spaces were built. As these musical practices evolved, a set of acoustical benefits evolved along with them benefits that helped both performer and audience to hear better. Our research shows that beginning in the late 1960s, these historically evolved benefits were largely lost in performances that used amplification. At that time, a different approach to amplification was being developed for very large audiences in stadiums and outdoor music festivals. This approach was then quickly adopted by musicians playing in venues of all sizes, including the small and medium sized venues in which the vast majority of performances take place. This paper examines the unintended problems introduced by this approach, and describes how they affect musicians ability to perform, and audiences ability to hear and appreciate the music. With these problems in mind, we show how a special application of a novel sound source can restore the historically evolved benefits of acoustic music to amplified performances Pinker, Steven, The Language Instinct: How the Mind Creates Language, Perennial Press. p. 214 (2ooo). White, Randall, Representation, Technology and Society Before Lascaux, first published in Archéologue-Nouvelle Archéologie, (1996). The Origins of Music, Ed: Wallin, Merker, & Brown; MIT Press, Cambridge / London (2ooo). Blood, A. & Zatorre, R. Intensely pleasurable responses to music correlate with activity in brain regions implicated in reward and emotion, Proceedings of the National Academy of Sciences, Vol. 98, No. 2o, (Sept. 2001)

3 U n a m p l i f i e d P e r f o r m a n c e s IN an unamplified performance, the arrangement in space of the players and their instruments creates a rich and diverse sound field. Musicians and members of the audience hear the sound of each instrument coming from a different direction, and this direction corresponds naturally to what they see. Extensive psychoacoustical research shows a significant improvement in clarity and audibility when sounds from multiple sources come from different directions. Other studies show the significant benefit that comes from being able to look at what we are listening to a benefit that is easily enjoyed when instrument sounds come from the direction of the instruments that make those sounds. 5 Furthermore, musicians in an unamplified performance play with the knowledge that the sound they produce on stage is the same sound that reaches their audience. The musicians are in complete control of their sound, and adjust their playing according to what they wish to project to their audience. Last, the equipment preparations required to play acoustically are generally modest. With few exceptions, moments after arriving, musicians are ready to play, and moments after they are finished, they are ready to leave. Their time is spent almost entirely on playing, not on preparing to play or preparing to leave. Considering all of these benefits, it is reasonable to conclude that the unamplified performance environment is one highly conducive to the creation and appreciation of music. These benefits have evolved over many thousands of years, and in general are enjoyed by acoustic groups of all kinds together with their audiences. 5 Sumby, W. H., and Pollack, I., Visual Contribution to Speech Intelligibility in Noise, Journal of the Acoustical Society of America, Vol. 26, No. 2, (March, 1954)

4 B r i e f H i s t o r y o f L i v e A m p l i f i e d M u s i c THE initial approach to amplification, introduced early in the twentieth century, was a natural extension to playing acoustically. This was the era of individual-instrument amplification, which was the dominant approach until the late 1960s. In this approach, a powered loudspeaker was used to increase the volume of certain instruments. For example, the guitar was amplified to add volume in situations where a purely acoustic guitar could not be heard in larger jazz bands for example. Frank Driggs Collection With the individual-instrument approach, instruments were made louder, but little else changed: the sound came from multiple directions; the sound came from the position on stage of the musician; musicians knew that the sound they produced on stage was what their audience heard; and the focus was very much on making music because the amount of equipment needed was still modest. In the 1940s and 1950s, popular new musical styles like Rhythm and Blues, Rock & Roll, and Soul were played at higher volume levels, and demand for live performances continued to increase. By the late 1960s, live amplified music was reaching larger and larger audiences. Bands and promoters alike struggled to entertain these larger crowds. For example, although The Beatles concert at Shea Stadium in 1965 was a huge commercial success, the audio system they used could not deliver the desired sound levels to the audience of 55,000 fans. The individual-instrument approach to amplification was clearly inadequate

5 The problem of filling large venues using the individual-instrument approach can be traced to a fundamental property of the loudspeakers used. These loudspeakers are very loud at close range, but they decrease rapidly in level with distance. 6 If the desired level is set on stage, it is too quiet in the audience, especially in a larger venue. Conversely, setting the desired level in the audience means exposing the musicians to painful sound levels on stage, and can lead to the uncontrolled squealing or howling sounds caused by excessive amplification. To solve this problem, another approach to amplifying live music was developed, and by the historic Woodstock Festival in 1969, four years after The Beatles played Shea Stadium, the sound-level-for-large-audience issue was being addressed by an approach we call triplesystem amplification. Although it was originally developed for large venues, by the mid 1970s the triple-system approach had become the standard for groups playing in venues of virtually any size, and it remains so today. The approach was to split the amplification system into three separate sound systems. The first system is comprised of backline instrument amplifiers. These amplifiers holdovers from the era of individual instrument amplification are mainly used to amplify electric guitars, keyboards, and basses. The monitor system consists of speakers aimed at individual musicians. Various voice and instrument signals are mixed together and sent to these speakers so musicians can hear themselves and some of their bandmates. The PA system consists of directional loudspeakers positioned at the sides of the stage and aimed towards the audience. The intent is to supply higher sound levels to the audience without radiating high levels to the stage. 6 In the field of physical acoustics, this is known as the inverse square law, whereby sound intensity drops by a factor of four with each doubling of distance from the source

6 P r o b l e m s w i t h t h e T r i p l e - S y s t e m A p p r o a c h IN a series of formal interviews, professional musicians told us that with triple-systems they routinely struggle to hear themselves and their fellow musicians on stage. They talked about the frustration of wearing earplugs because sound levels have become so dangerously loud. They complained that they feel totally isolated and have no idea what their audiences are hearing. And they spoke at length about the time-consuming and technically complex process of setting up and sound-checking their equipment. Audience members told us that lyrics are often difficult or impossible to understand, and that instrument sounds are garbled or simply missing. They reported that they are often left with their ears ringing after a performance, and feeling that the sound was so unpleasantly loud that any beauty or detail in the music was lost. A team of engineers and technicians at Bose Corporation spent ten years researching the source of these complaints. Our results show clearly that triple-systems solved one problem achieving higher sound levels in the audience area without making it too loud on stage but created many others by erasing the historically evolved benefits of acoustic music. In the following analysis, we use the principles of acoustics and psychoacoustics to show how these problems make it much harder for musicians to play well, and much harder for audiences to hear and appreciate the music. L o s s o f a u d i t o r y - v i s u a l i n t e g r a t i o n We instinctively try to connect what we hear with what we see by turning to face the sound we hear. We know from many studies that when we do this, we gain a much deeper understanding and appreciation of whatever it is that has caught our interest. 7 Connecting what we hear with what we see also enhances our appreciation of music. In an acoustic music performance, if we hear something of particular interest, such as a solo, we naturally turn our heads to connect sight with sound. 7 See, for example, Sumby, W. H., and Pollack, I., Visual Contribution to Speech Intelligibility in Noise, Journal of the Acoustical Society of America, Vol. 26, No. 2, (March, 1954), or Massaro, D. W. and Stork, D. G. Speech Recognition and Sensory Integration American Scientist, May-June

7 In the triple-system approach to amplification, however, the voices and instruments are electronically combined and emanate from a single location: the nearest PA speaker for the audience, and the nearest monitor speaker for the musician. Neither musician nor audience member can easily connect what they hear with what they see. Instead we found that audience members become distracted visually searching for which musician is making the interesting sound. And musicians reported that under these circumstances, it is easy to lose critical music cues and miss out on the musical ideas of their fellow players

8 L o s s o f d i r e c t i o n a l i n f o r m a t i o n In the field of psychoacoustics, there is a fascinating and much studied property of human auditory perception called the cocktail party effect. 8 We rely on this property in environments where there are many competing sound sources. At a cocktail party we can close our eyes and concentrate on any one talker, and usually understand what they are saying. We can turn our attention to a talker on our left, for example, and hear and understand them. Or we can turn our attention to someone on the right, and understand that talker. However and this is the crucial point if those two talkers are moved next to each other so that their voices come from a single direction, we know from many studies that our ability to distinguish what either one is saying is greatly diminished. In an acoustic-instrument performance, the benefits of the cocktail party effect are preserved because we hear the sound of each instrument coming from a unique direction. For example, in a string ensemble, we might hear the violin from our left, the viola from leftcenter, the cello from the center-right, and the harpsichord from the right. Sound arriving from different directions produces significantly different responses at the two ears, and these differences form the raw material our hearing system uses to differentiate individual sources in a multi-source environment. In the triple-system approach, however, a mixing console electronically combines voices and instruments into a single composite signal. This signal is then amplified and sent to the PA speakers, which project the mixed sound to the audience. In such an arrangement, the audience hears all of the voices and instruments coming from the direction of the nearest PA speaker, 9 and thus cannot benefit from the cocktail party effect. The same situation is true on stage for the musicians, where signals from multiple instruments are electronically combined and emanate from a single direction: the monitor speaker closest to the musician. They too are unable to benefit from the cocktail party effect. We found that the loss of spatially distributed sound sources in triple-systems is one important reason musicians complain of not being able to hear well from their monitors. This problem also contributes to audience complaints of hard-to-hear lyrics and garbled instrument sounds. 8 9 See, for example, Bronkhorst, A., The Cocktail Party Phenomenon, Acustica, Vol. 86 (2ooo), pp Although both PA speakers are on, we localize to the nearest one because of a property of our hearing called the precedence effect. For more on this property, see for example, Cremer, L., and Muller, H., Principles and Applications of Room Acoustics, Volume 1, p

9 E x c e s s i v e r e v e r b e r a t i o n We found triple-systems often create excessive reverberation, which is well known to make lyrics more difficult to understand and to diminish musical detail. 10 The three independent speaker systems flood the room with sound, much of which strikes the upper walls and ceiling, and returns to listeners as reverberation. Monitor speakers are especially problematic when it comes to generating reverberation. Pointed towards the back wall and angled upwards, they reflect sound off the back wall and ceiling, and then into the listening area of the room. 10 For a good introduction to the effects of reverberation on speech, see Steeneken, H. and Houtgast, T., A Review of the MTF Concept in Room Acoustics and its Use for Estimating Speech Intelligibility in Auditoria, Journal of the Acoustical Society of America, Vol. 77, No. 3 (1985)

10 A c u t e d i r e c t i o n a l i t y o f b a c k l i n e i n s t r u m e n t a m p l i f i e r s Backline instrument amplifiers are the source of some remarkable musical instrument sounds, especially from the electric guitar. But we found that they are also the source of some very serious acoustical problems. We observed that guitar players almost never stand right in front of their backline amplifiers. Musicians told us the reason is that these speakers are so directional that the sound level and tone directly in front is very harsh. But some audience members are inevitably on axis and get excessive, often unpleasantly loud guitar sound. Musicians told us they experience the same effect. If they are on axis of the guitar beam, the sound is harsh and dominating. If they are off axis, they hear only a dull version of the instrument a version that guitar players say is unrepresentative of the tone they have carefully created. We came to the conclusion, therefore, that the only one getting the correct guitar sound in a triple-system environment is the guitarist

11 L o s s o f a r t i s t i c c o n t r o l In the triple-system approach, a mixing console is used to mix voices and instruments one way for the audience via the PA speakers and another way for the musicians via the monitor speakers. These separate mixes are created by a sound operator typically positioned in the audience. In this arrangement, the musicians initiate the sound, but then they immediately lose control of it to the person operating the mixing board. They do not control how they sound to themselves through their monitors, nor do they control how they sound to their fellow musicians. And yet the person who does have this control (the sound operator) cannot hear the monitors because they are not on stage. It should be no surprise that one of the most common things we heard from musicians was frustration with the sound in their monitors. Furthermore, because the directional PA speakers are deliberately aimed away from the stage, the musicians hear little, if any of the sound that s being created for their audience. Musicians simply cannot know how the sound operator has changed their sound, and therefore cannot know if their artistic intent has been met. The musicians we worked with said that their assumptions about the sound in the audience are often wildly incorrect, something they said they only discover after the performance by asking people, How did we sound? The triple system approach to amplification is responsible for an enormous loss of artistic control. E x c e s s i v e l o u d n e s s In our research, we found that the problems already described the difficulty of connecting what is heard with what is seen, the inability to use the property of the hearing system known as the cocktail party effect, the problem of excessive reverberation, and the loss of artistic control all help explain why musicians complain about not being able to hear themselves and each other. Musicians told us that when they are struggling to hear and be heard, they naturally react by increasing their volume. And when multiple musicians react this way, the music gets louder and louder to the point that an increasing number of musicians and audience members are wearing earplugs during performances. In addition to the well-established relationship between excessive sound levels and permanent hearing damage, 11 it has been shown in psychoacoustical studies that at higher sound levels, listeners ability to hear detail and understand lyrics is seriously diminished. 12 The irony, then, is that musicians are increasing their volume to hear better, but when they do, they are in fact hearing even less well. 11 For a good introduction to hearing loss from excessive sound levels, including amplified music, see the information provided by the House Ear Institute at 12 See, for example, Pickett, J. M. and Pollack I., Masking of speech by noise at high sound levels, Journal of the Acoustical Society of America, Vol. 30, No. 10, pp

12 A m o u n t a n d c o m p l e x i t y o f e q u i p m e n t In the triple-system approach, there are numerous speaker enclosures, power amplifiers, mixing consoles, and electrical cables. Musicians told us that it is a major effort to load the equipment into a vehicle (or vehicles), transport it to the venue, then unload and carry it to the performance area. After load in and set up, hours of work are usually required to wire all the equipment together. Cables are needed to connect instruments to backline amplifiers and mixing consoles, mixing consoles to amplifiers, and amplifiers to speakers. All of the connections must be checked and any problems detected and repaired if possible before the performance. And then the whole process must be repeated in reverse after the performance is over. Before triple-system amplification, we estimate that musicians spent approximately 90% of their time playing and only 10% on the equipment necessary to play. Today, we estimate that ratio has been reversed. This has an obvious impact on musicians ability to improve their playing because equipment requirements seriously reduce rehearsal and practice time. Additionally, triple systems consume valuable space on stage. We found that musicians are often confined to very small areas, literally boxed in by their sound equipment. And once set up, the equipment often obscures sight lines between audience and stage, thereby reducing the number of good viewing locations in the audience

13 A N e w A p p r o a c h WITH the problems of triple-system amplification in mind, a group of researchers at Bose Corporation pursued a new approach to live music amplification an approach that restores the natural and historically evolved benefits of acoustic music to performances with amplification. To understand the insight that led to the new approach, recall that a conventional loudspeaker radiates sound in three dimensions: out, left and right, and up and down. It is well known that such a source retains only one-fourth of its sound intensity with each doubling of distance from the source. We hear this as a rapid reduction in sound level with distance. The problem is that if a comfortable level is set on stage for the musicians, the sound is often not loud enough in the audience area. Conversely, if a comfortable volume level is set in the audience, it is uncomfortably loud on stage. It is this fundamental property that makes conventional loudspeakers unsuitable for the challenge of creating sound for both the musician and the audience at the same time without being too loud or soft for either. It was senior research engineer and keyboardist Clifford Henricksen who first suggested using a Cylindrical Radiator T M loudspeaker to address the problems of amplified music. He made an early prototype, and its performance was deeply impressive to all that heard it, including a group of engineers who were also semi-professional musicians. We found that we could set the correct level in the audience and then move to the stage area and hear the level as increasing only modestly. We could walk to within inches of the prototype and never have the feeling that it was too loud. Henricksen and others immediately set out to further test and refine the concept

14 With this new loudspeaker, Henricksen knew that there was no longer any justification for separate backline, PA, and monitor systems. Several Cylindrical Radiator T M loudspeakers roughly one located behind each musician replace all three systems. Notice how the approach closely approximates the acoustics of an unamplified performance: the sound of each musician comes from the location of that musician, the musician alone controls his or her tone and volume, and only a small amount of equipment is needed. With these insights in mind, a team set out to refine the approach. A number of acoustical prototypes and musical performance tests were conducted to optimize the performance of the Cylindrical Radiator loudspeaker. For instruments that require amplification in the bass and baritone ranges the bass guitar or electronic keyboard for example the team developed a separate loudspeaker enclosure to accompany the Cylindrical Radiator loudspeaker

15 A powered stand was made to support the loudspeaker and house power amplification and electronics. The devices were made compact and easy to disassemble, making them very portable. Electronics were designed to allow a microphone, musical instrument, or other piece of audio equipment to be connected directly to the powered stand. Another generation of prototype systems was tested with a variety of musical groups and in a variety of venues. In each case, professional musicians were given a brief presentation of the technology, and were then aided by technicians during the normal pre-performance preparation period. An audience was invited; however, these individuals were deliberately not told of the new technology because the researchers wanted an authentic audience reaction. A number of musical styles were tested: Rhythm & Blues, Rock n Roll, Country, Folk, Pop, Soul, Alternative, Blues, and Jazz, among others. Similarly, a number of venue types were tested: small club, medium nightclub, large nightclub, small and large function rooms, civic auditorium, small performing arts theater (5oo seats), and large performing arts theater (conventional PA speakers were used to fill distant seating areas). The results were an extraordinarily strong validation of the concept. Musicians spoke of a quantum improvement in their performance because they could hear themselves and each other. They were excited to be in complete control of their music, and appreciated the reduction in the amount and complexity of equipment. Many noticed that they were playing with greater dynamics (from very soft to very loud passages). The urge to turn up their volume was gone and thus the overall stage volume remained comfortable. They described the experience as being completely natural more natural than anything they had experienced before in an amplified performance. Audience members participating in the testing said they were thrilled by the clarity of voices and instruments. And they described sound that was exciting and dynamic but not excessively loud. A final prototype of the Cylindrical Radiator T M loudspeaker was built and additional tests conducted with musicians and audiences. Final refinements were made, and the product was engineered for manufacturing

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17 F u n d a m e n t a l A d v a n t a g e s o f t h e N e w A p p r o a c h THE approach based on the Cylindrical Radiator T M loudspeaker addresses problems created by the triple-system approach, and restores the historically evolved benefits of acoustic music to performances with amplification. The advantages of this approach benefit both musicians and audiences. 1. R e s t o r a t i o n o f a u d i t o r y - v i s u a l i n t e g r a t i o n In the audience and on stage, the visual and auditory fields are synchronized. Sounds come from their proper directions. As a result, musicians and audience members can quickly use their eyes and ears together, which is known to deepen their musical experience. 2. R e s t o r a t i o n o f t h e p r o p e r t y o f h e a r i n g k n o w n a s t h e c o c k t a i l p a r t y e f f e c t The full benefit of the cocktail party effect is enjoyed by musicians and members of the audience. The sound of each instrument or voice comes from a different direction, and can therefore be heard and understood better. Listeners can pick out and appreciate individual instruments and voices even in highly complex passages. 3. L e s s r e v e r b e r a t i o n Cylindrical Radiator loudspeakers radiate very little sound to the upper walls and ceiling, and therefore create less reverberation. Our testing showed that instrument sounds were clearer, and vocals more intelligible. Moreover, we found that Cylindrical Radiator loudspeakers significantly reduce the undesirable variation in sound that performers experience as they move from venue to venue. 4. C o n s i s t e n t s o u n d q u a l i t y t h r o u g h o u t t h e l i s t e n i n g a r e a As an amplifier for musical instruments and voices, the Cylindrical Radiator loudspeaker has fundamentally superior properties. Instead of radiating a beam of sound outward toward only one player, it radiates sound almost equally to the stage and audience areas. In testing, players reported that they heard themselves better, heard fellow players better, and did not need to stay fixed in one location on stage to hear good sound. 5. C o n t r o l o f m u s i c r e s t o r e d t o m u s i c i a n s The musicians and no one else are in complete control of their music, as in an acoustic performance. In testing, musicians reported that they were able to play with confidence, knowing that the sound they made on stage was what their audience heard. They said they were able to play naturally, mix themselves, and make adjustments to their playing to optimize their performance

18 6. C o m p a c t, e a s y - t o - u s e e q u i p m e n t Cylindrical Radiator loudspeakers require a relatively small amount of cargo space, and are easy to transport and set up. Assembly takes about a minute. Then, the musician simply plugs in and plays. The only electrical cords are from the instrument or microphone to the speaker, and from the powered stand to a power outlet. Sightlines between stage and audience are unimpeded. 7. C l e a r, d i s t o r t i o n - f r e e s o u n d Musicians and audiences hear sound from the Cylindrical Radiator loudspeaker that is free from unwanted distortion. Intentional distortion for example from an electric guitar preamplifier or guitar modeler is faithfully reproduced. 8. I n c r e a s e d d y n a m i c r a n g e Testing of this new approach showed that musicians play dynamically but at lower average volume levels. The urge a musician feels to increase his or her volume is greatly diminished because of the improvement in clarity and detail. Audiences experience music that has an increased dynamic range without enduring uncomfortably high sound levels. C o n c l u s i o n THROUGH extensive acoustical and musical-performance testing, it is now known that a unique type of sound source arranged in a special and naturalistic way significantly improves live amplified musical performances. The application of the Cylindrical Radiator T M loudspeaker approximately one for each musician on stage allows the long-evolved benefits of the unamplified musical performance to be experienced with musical styles that use amplification. First Edition 2004 Bose Corporation. All rights to illustrations and text reserved by Bose Corporation. This work may not be copied, reproduced, or translated in whole or in part without written permission of Bose, except for brief excerpts in connection with reviews or scholarly analysis. Use with any form of information storage and retrieval, electronic adaptation or whatever, computer software, or by similar or dissimilar methods now known or developed in the future is also strictly forbidden without written permission of Bose. A number of photographs are reproduced by permission