Ten Ways to Voice a Room
Have you noticed that your newly purchased piano doesn’t sound quite the same as when you tried it in the showroom? The difference you notice between showroom and home may stem from the acoustics of the room in which the piano is placed. Not all problems with piano tone are best solved by voicing the instrument—it may be your room that needs voicing. Some of the factors that can significantly affect the sound of your piano room are: the size of the room, including ceiling height; the sound-absorbing and -reflecting materials in the room, which give it its reverberant character; and the number and orientation of objects in the room, which affect how sound is scattered or diffused.
Making the Distinction Between the Piano and the Room
It’s important to distinguish between acoustical problems caused by the piano and those caused by the room. For instance, a problem of too much loudness is often caused by a piano that is too large for the room. This can be best addressed at or close to the piano, rather than by increasing the amount of sound-absorbing materials elsewhere in the room. On the other hand, such problems as harshness of tone, excess lingering sound, and hot and dead spots, can often be attributed to the room. Many of the following suggestions for loudness control or other acoustical adjustments are easily reversible; experiment with some of these before making more permanent changes to your piano or room.
Reverberation refers to the persistence of sound within a space after the source of the sound has stopped. Such prolongation of sound can help give music the qualities of blending, lushness, fullness, and breadth. Too much reverberation can make the music muddy and indistinct, and the buildup of reverberant sound can make the piano sound too loud. When there is too little reverberation, the room is said to sound “dry” or even “dead”; to compensate for this, the pianist might feel the need to overplay to achieve a lush, musical sound. In general, the larger the cubic volume of the space, the longer the reverberation time; the smaller the cubic volume, the shorter the reverberation time. The more sound-absorbing materials in the space, the shorter the reverberation time; the fewer such materials, the longer the reverberation time. The length of reverberation is a matter of personal preference. Some pianists like having the room reverberation be part of the sound of their piano playing; others prefer keeping the sound of the room to a minimum, enjoying primarily the clear sound of the piano as modulated by their technique.
Hot or Dead Spots
Hot spots and dead spots are places in the room where certain frequencies or notes, though played with the same force, stand out more than other frequencies or notes. Problems of this type are best solved by installing sound-scattering objects: bookcases, furniture, wall hangings, and so forth. Reorienting the piano or moving it slightly can also help.
Below are ten ways to mitigate problems in piano sound other than by voicing the instrument, beginning with some relatively simple things to do nearby the piano itself:
Buy a piano that’s the right size for the room.
The first and best way to avoid problems with room acoustics is to buy a piano that’s the right size for the room. Too large a piano can overload a room with sound, while one that’s too small may not be heard equally well in all parts of the space. A rule of thumb: Assuming a ceiling height of eight feet, the combined lengths of the four walls should be at least ten times the length of a grand piano or the height of a vertical. However, it’s not always possible to follow this advice—in many cases, the purchase decision will be dictated more by musical needs or budget than by room size. A small piano, for example, may have performance problems inherent to the instrument’s size, such as poor bass tone or an unresponsive action, even when it’s the right size for the room. Or, if you’re longing for a large grand’s growling bass, be aware that, even though such a piano is perfectly capable of producing that sound, your room may not be able to support it.
When the piano’s size is not a good match for the room, try voicing the piano, or experimenting with one of the following tips:
Move or reorient the piano within the room.
Most rooms have three pairs of parallel surfaces: two sets of opposing walls, and the ceiling and floor. Parallel surfaces tend to produce standing waves—certain frequencies that sound much louder than others at some points in the room, but that are virtually inaudible at other points. Moving the piano away from room corners and partway along the length of a wall, and/or turning it at an angle this way or that, can sometimes mitigate this problem. You’ll have to experiment, listening at different places within the room. Remember that the piano’s sound when you sit at the keyboard will be different from its sound elsewhere in the room.
Use a piano cover to directly reduce loudness.
Typical cloth string covers designed for grand pianos—that is, covers that lie directly on the strings—will only marginally reduce sound volume, especially if they have only a single layer of cloth. Most reports say that thin string covers are effective only for the highest notes, to take the edge off the sound. Thicker, sound-attenuating string covers, custom-made for a particular model of grand piano, work better. An even more effective mute for a grand would be a full-size, quilted cover that reaches the floor. However, this will require closing the lid completely and placing the music rack atop the cover—though unattractive, in some situations this is the only practical way to reduce excess loudness. For a vertical piano, a blanket or section of carpet can be attached to the piano’s back.
Place sound-absorbing material inside the piano, between the soundboard and the wooden structural support beams.
You may be able to drastically reduce a piano’s loudness by inserting blankets or foam rubber blocks between a grand’s soundboard and its wooden case beams, or between a vertical’s soundboard and wooden posts. One possibility is to purchase the foam in sheets and cut shapes to fit. Your piano technician may have experience in doing this, and may also be able to help you avoid damaging the soundboard or creating the buzzes that can accompany this technique—ask for pointers. This method of loudness control won’t be possible if you have a grand outfitted with a humidity-control system or an electronic player-piano system.
Place a rug under a grand piano to absorb sound.
The sound of a grand piano is sent out into the room via the lid, which is propped up at an angle on the stick—and by a considerable reflection by the floor of sound emanating from the underside of the soundboard. If your floor covering is a sound-reflecting material such as wood, stone, or tile, the loudness can be greatly reduced by placing a rug under the piano. To absorb even more sound, place a thick pad under the rug. Experiment with the size of the rug or carpet and its orientation under the piano. Other, more temporary solutions: place a dog bed or a collection of throw pillows under the piano.
Place objects under a grand piano to scatter sound.
Perhaps you don’t want to absorb the sound coming out of the bottom of your grand piano, but just want to disperse it more evenly throughout the room. The space under a grand can be used for storage chests, plants, knickknacks, and the like.
Let’s say you’ve tried some or all of these steps; you’ve noticed some improvement, but not enough. Here are some more advanced treatments for the room itself.
Cover or expose hard wall and/or window surfaces.
Glass tends to reflect high-frequency sound, while allowing lower frequencies to pass right through, never to return. A room with a lot of exposed glass will often sound harsh and bright, as if the treble notes are accentuated, but the problem may in fact be a lack of bass energy, or an imbalance between the bass and treble energy in the space. Covering these windows can help to absorb higher-frequency sound energy and thus restore the balance of bass and treble. Heavy fabric such as velour, sewn into gathers, works best to absorb sound. Sheer, semitransparent fabrics are much less effective, but can have subtle acoustical effects, if that’s all that’s required, and can be used to “fine-tune” the room.
Large areas of exposed bare walls and ceiling can produce a similar effect as glass, but are more effective at preserving bass energy. In a room that sounds too muddy—i.e., it makes music sound indistinct—sound-absorbing wall coverings such as tapestries, or hanging rugs, might be worth a try. Also available are fabric-wrapped, sound-absorbing panels that will work well in homes, though their “professional” look lacks the personal touch of one’s own home furnishings.
In a space with high ceilings, hanging banners, flags, or other materials from the ceiling can cut down on reverberation.
Be aware that most household sound-absorbing materials do not work very well below about 200 Hz (about middle C). If your acoustical problem occurs below this frequency, look to other techniques or materials to solve it, including professional acoustical materials designed specifically to address low-frequency sound.
Add or remove upholstered furniture and other sound-absorbing objects.
Adding sofas, pillows, upholstered chairs, carpets, and other sound-absorbing décor can reduce excess reverberation and loudness, and removing such objects will increase them. Even placing cloths over coffee and side tables will cut down the reflection of sound just a little bit. Plush, overstuffed furniture produces the greatest sound-absorbing effect. Upholstered furniture of leather, wood, or metal has less effect.
Add or remove sound-scattering wall hangings, objects, and furniture.
Be careful not to add too many sound-absorbing objects to the room—it’s possible to go too far, making the room sound too dead, dry, or soft. Sometimes you don’t want to absorb sound—you merely want to scatter or diffuse it more evenly about the room. The sound will then be more natural and less “hollow” without necessarily losing reverberation and loudness. In scattering sound, your goal is to use objects both large and small with complex shapes to break up large expanses of flat surfaces. Again, some experimentation is in order. Examples of sound-scattering objects are bookshelves (not too full), tables, chandeliers, room-dividing screens, and sculpture. Designing a space with ceiling beams can also scatter sound.
You’ve tried everything! Below is one last word of advice.
Hire a professional.
Some of the acoustical phenomena described here can be confusing to the untrained. Even worse, some problematic combinations of piano and room may have more than one of these problems. If you’ve tried everything and still don’t hear an improvement, consider seeking expert help from a piano technician or a room-acoustics consultant (acoustician). Such professionals may be able to help you design or furnish the space for the best sound, suggest appropriate acoustical materials, and direct you to local suppliers for those materials.
Chris Storch, RPT, is an acoustician with 25 years’ experience in the areas of architectural acoustics, noise and vibration control, and environmental noise abatement. Some of the more prominent projects on which he has consulted include Verizon Hall, in Philadelphia; Sibelius Hall, in Lahti, Finland; LG Arts Center, in Seoul, South Korea; and Fox Cities Performing Arts Center, in Appleton, Wisconsin. Storch is a 2009 graduate of the Piano Technology program at the North Bennet Street School, in Boston. He tunes and services pianos in the Boston area, and conducts research in piano acoustics in his spare time. He can be reached at [email protected].