The music industry is witnessing staggering electronic advances in digital recording, new 5.1 surround delivery formats, DVD, etc. However, to appreciate all of this potential we must remember that sound eventually travels the acoustic analogue path from loudspeaker to our ears. Our auditory system, ear and brain, processes the direct sound from the loudspeakers and the torrent of early and late arriving reflections from the room and synthesizes a pyschoacoustical sensation of what we are hearing. What we hear depends on the complex interaction among the electronics, the hearing quality and placement of the listener in the room, the quality and placement of the loudspeakers, the dimensions of the room and the general acoustic condition of the room and its contents. Thus in addition to the electronic distortion you may be familiar with in hardware terms, the interaction of the sound and the room can introduce what we call "acoustic" distortion. This complex electro-acoustic interaction is often overlooked and emphasis is placed solely on the quality of the hardware.
Sound Production Room
Sound production rooms acoustically contribute to the perceived sound of the music or speech. The arrival time, direction and temporal density of the early reflection pattern, coupled with the various early to late energy ratios and decay time, level and temporal and spatial density of the late reflections define the sound that heard. If we listen to a cello recorded in an anechoic chamber, devoid of any reflective surface, it seems dull and lifeless. When the instrument is placed in a performance environment it takes on the warm and reverberant sound we come to expect from a cello. Therefore, the sound we hear is a combination of the instrument and the sound production room.
Sound Re-Production Room
Sound reproduction rooms, on the other hand, like recording studios and home theaters, should be neutral. All of the spectral, timbral and spatial information is pre-encoded on the playback media and the room's only function is to allow a critical listener to hear what has been recorded, as is was recorded. As opposed to a music production room, a music re-production room can only add acoustical distortion and corrupt the music reproduced. Therefore, it does not add to the music as a music production room does.
Recording Session
Since the founding of RPG in 1983, we have attempted to document the complex electro-acoustic interaction occurring in listening rooms, via journal publications, magazine articles and seminars. However, at the end of the day, hearing is believing. Therefore, we thought we would try to create Acoustic Demonstrations to illustrate the effect the room can have on what we hear. There is certainly a need for scientific audiology/test demonstration discs, but in this case we wanted to create demos that were both enjoyable to listen to and also informative, not a series of test tones.
The Room
To study the effects of the room on what we hear, we built a dedicated listening evaluation lab at RPG with dimensions 19' (L) x 14' (W) x 10' (H), for good modal distribution. The room was constructed on a concrete floor with wood stud construction. The inner walls and ceiling consist of 3 layers of damped 5/8" drywall that were glued, screwed and caulked. The stud core was filled with honeycomb and the outer skin was 3/4" MDF. The inner surface was painted. The room is solid!
The goal of the treated rooms was to provide good imaging, using absorptive
and diffusive image tools; provide uniform distribution of the sound using
diffusion tools and provide a uniform frequency response using bass trapping
Bass tools; and finally to provide a uniform reverberant decay response.
The MusicOur friends at Telarc, Pope Music, DMP and Q-up Arts graciously allowed us to use commercial CD releases for these tests. Buck Brown also provided an excellent live guitar performance.
The Equipment
Speaker and microphone positions were determined using RPG's Room Optimizer™ software program to minimize the speaker-boundary interference and modal excitation.
Since much of what we hear can be corrupted by very low level effects, we felt we needed to use the latest 20 bit recording technology to faithfully
reproduce
the sound in the room. To accomplish this, we turned to our friends in the
recording industry who are at the cutting edge and responsible for much
of the music you hear. In a weak moment, after several informal discussions,
my friend Tom Jung of DMP, graciously volunteered his talents to record
and edit the session. Tom also supplied all of his own recording tools as
well. Without his help and encouragement, this project would never have
been possible. The CD musical selections were transferred and edited to a DAT. The DAT signal was fed to a Parasound amplifier, which drove two Paradigm Studio/20
loudspeakers.
The reproduced signal in the room was recorded with multiple Shure microphone
configurations, a Grace 801 Preamp, Benchmark 2004R A/D converters and the
Yamaha DRU8. Upon editing, the ORTF configuration using two Shure SM81 microphones
most faithfully represented what we heard in the room. The tracks were edited
using Samplitude software and transferred to a CDR. The Demonstration
We explored the effect of acoustics on several types of rooms- a project studio, a home theater, a conference room and a music practice room. For each room type we created:
1. A direct digital CD transfer, which is the reference of what the musical passage originally sounded like
2. A recording of the musical passage in the untreated very reverberant room (unpainted drywall walls and ceiling and concrete floor)
3. A recording of the musical passage in the RPG acoustically treated room
Therefore, each musical passage is repeated three times (reference, untreated, and treated). The idea was to allow the listener to hear them in sequence. Then at the listener's discretion he/she can switch among the three musical passages in any desired order.
This research project yielded much interesting information and musical samples. We begin by presenting three selections: instrumental piano in a small Jazz ensemble, folk vocal and a symphonic selection. All selections were recorded in a home theater type of setting.
NO ARTIFICIAL REVERBERATION OF ANY KIND WAS ADDED TO THIS RECORDING! We mention this because you may be astonished at the sound of the untreated room!
Conclusions
The goal of these experiments was to see how faithfully a room could
reproduce
the inherent sounds recorded on a CD. You will find that the untreated room
introduces significant reverberant acoustical distortion. On the other hand,
the RPG treated room very faithfully reproduces the original CD sound provided
as a reference, despite the fact that a commercial CD was played back through
a speaker/amplifier reproduction system, re-recorded in the room, edited
and re-mastered. Play the CD reference sample followed by the sample re-produced in each type of room treatment, switching back and forth, to gain an appreciation of the changes introduced by the room acoustics. It is remarkable the extent to which a properly treated room can reduce acoustical distortion and accurately reproduce music.
Sample One
~177K Download
Artist: Warren Bernhardt
Label: DMP 468
Album: Heat of the Moment
Cut: Walkin' Up
Motif: Instrumental Piano
Sample Two
~177K Download
Artist: Lori Libermann
Label: PM 1005-2
Album: Home of Whispers
Cut: Roots and Wings
Motif: Vocals Folk
Sample Three
~177K Download
Artist: Baltimore Symphony Orchestra
Label: Telarc 80270
Album: Stravinsky The Firebird
Cut: Finale
Motif: Symphonic
Home:
Listen
to the Music, Not the Room!
|
|
|
|
| Copyright 2000, RPG Diffusor Systems, Inc. |