Research and Development

Sound-Field Control Panel (Articulation Panel)

A sound field can be defined as the acoustic profile of a given space. While many people are unfamiliar with the concept, sound fields are environmental realities that play a significant role in everyday life. For example, your living room is comfortable because it has a sound field that is conducive to relaxation. A concert hall, in contrast, has a sound field that is more appropriate for musical performance, allowing for stress-free musical enjoyment.

What happens when you find yourself in a space that does not have an appropriate sound field for its purposes? Have you ever sat in a conference room where voices sound muddy and muffled by reverberations? Or perhaps you remember sitting in a large gymnasium as a student and struggling to hear the instructor's words or to project your own? These are cases where the sound field is unsuited to the task at hand. The reason we don't hold conferences in spaces that sound like the inside of a tunnel is precisely because a tunnel's sound field is completely inappropriate for this purpose.

In the past, it was no easy matter to adjust a room's sound field to a given purpose—whether for relaxing, playing music, or holding a meeting. The task would typically require study and design by an acoustics expert, followed by some serious construction work. Small rooms are the most troublesome: they tend to have poor sound fields in the first place, and their size limitations restrict the types of adjustment that can be made. It has been particularly difficult to improve the acoustics for lower frequencies, as such adjustments typically require the use of thick walls or other thick materials.

Yamaha has addressed these problems by developing a sound-field control panel that enables easy adjustment of the sound field without the need for an acoustics specialist. The panels are light and thin, and are capable of resolving sound problems in many different environments. All that is necessary is to mount them on the wall. They can deliver well-balanced adjustment over the full frequency range—from low to high—and are therefore suitable for conference and meeting rooms as well for musical performance spaces.

Basic Technologies

Absorption Profile and Sound Dispersion

The panel's sound absorption profile adjusts the reverberation to a level appropriate to the room, while its sound scattering properties improve sound quality and eliminate acoustic defects. Anyone can easily use these panels to adjust the room's sound field so as to secure a better and more suitable sound.

The sound absorption profile is the degree to which the walls absorb rather than reflect the sounds that impact them. A living room or concert hall will deliver suitable sound only if its walls have an appropriate absorption profile, with neither too much reflection nor too much absorption for the purpose at hand. And this absorption must be correctly balanced: if the higher frequencies sound too shrill or the lower frequencies sound to muddy, then the profile needs adjustment.

Rooms may also suffer from acoustic defects, resulting in the production of unpleasant sounds.
Well-known defects are boominess, or excessive reverberation of lower frequencies, and flutter echo, characterized by hissing and clicking echoes.

The following video presents simulations of these two acoustic defects. (You can hear these more clearly if you listen through headphones.) As the video demonstrates, good sound sources (good instruments, speakers, and so on) are not sufficient in themselves to get good sound; you also need an appropriate sound field that correctly conveys the sound to the listener.

Yamaha's sound-field control panels can be used to adjust the sound field and suppress these acoustic defects.

The control panel offers a superlative absorption profile, in part because its frequency absorption characteristics are flatter than those of other materials and therefore easier to work with. These panels make it easy to achieve effective adjustments, with no need to work out the complicated configurations that would be required with other adjustment aids.

For example, glass-wool panels offer good absorption of middle and high frequencies, but do not deliver sufficient absorption of the lower frequencies that largely define the male voice. When used alone, therefore, glass-wool panels will actually impair, rather than improve, the reverb frequency balance. Proper balance is crucial to achieving an effective sound profile.

Multiple Acoustic Resonance Tubes

The sound-field control panel is a series of conjoined hollow tubes. Each tube has a single slotted aperture on one side, effectively causing the section of the tube above the aperture and the section below the aperture to function as two resonating pipes. Each tube absorbs and disperses the specific frequencies corresponding to the length of these pipes, as determined by the aperture position. The sound field is adjusted by correctly arranging these apertures and tubes.

The panel essentially operates as equalizer adjusting the frequencies that correspond to each tube. Because the panel consists of ten tubes, it works over a wide frequency range. Using the panel to optimize the sound field is just about as easy as using an equalizer to adjust audio playback.

A Thin Design That Works Even on Low Frequencies

Until now, materials used to adjust the low frequency range (up to 125 Hz) required a thickness of about 500 mm (19.7 inches) and were difficult to work with and arrange. The prototype for the sound-field control panel, however, is only 30-mm (1.2 inches) thick. With a width of 600 mm (23.6 inches) and a height of 900 mm (35.4 inches), the panel weighs only 4 kg (8.8 lbs) and can easily be carried and positioned by a single adult. You can set the panel up in a conference room to improve the audibility of speech, or in a music-performance room to create more pleasing acoustics. These panels make it possible to quickly deliver room acoustics that once would have required significant expense and specialized design to achieve.

Return to Top