Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum How much difference does hardwood floors make in sound?

Andy,

There are too many pavilions to count with this problem - Bank of America pavilion in Boston...Caramoor in New York....
The Aspen music tent is one example of how the tent was done well.

They do make a sound-absorbing inner liner for these tension-membrane roofs. They double the weight, causing a structural issue. And they double the cost. And the roof has to be replaced every 10-15 years.

See why they overlook any acoustical deficiencies?

Chris S.

No. You're confusing two principles. In general, increased mass is used as a way to BLOCK sound from going from one space to the next through a wall or floor. Blocking sound is difficult at low frequencies, and requires special techniques which may include increasing the mass of the partition separating the two spaces. Sound is ABSORBED by thick, porous materials, generally with very little mass. Absorbing low-frequency sound is also difficult, and requires its own set of special techniques (bass traps, membrane absorbers, etc.).



Now you're talking about room modes, which is entirely different than the previous two principles. Room modes occur when a wavelength of a particular frequency of sound corresponds to the physical dimensions of the room in question. They most often occur between parallel surfaces (there are three pairs usually in any given rectangular parallelpiped space), and can occur at integer mutiples of the fundamental frequency. The resulting audible effect one hears from room modes are hot spots and dead spots in particular locations at specific pitches. One can try and reshape the surfaces to avoid the parallelisms, make the surfaces sound-absorbing instead of sound reflecting, change the surfaces to sound-scattering, or just tolerate it. Steinway's selection room at the New York factory has one wall that's canted out of perpendicular, I presume to avoid the room modes between the parallel walls. Again, as an acoustician, I'm bemused because the other pair of walls is still parallel and the floor is parallel to the ceiling.

There are room mode calculators on the internet. They generally identify the room modes for rectangular parallelpiped spaces. These are the tools many recording studio designers like to use, but they don't have much practical application to the real-world living rooms we work in. One can also go to a built space and measure the room modes, but you wouldn't use noise for that.

I once had a client who was really disturbed by the room modes he heard in his living room. When I told him what was needed to correct the problem, he quickly decided he'd learn to live with the room modes. He moved the position of the piano to get his head out of the acoustical hot spot he was hearing, and then promptly found another hot spot at another pitch.


Again, I'm bemused at caster cups being sold as some kind of vibration isolation for pianos. Some of the hard plastic or wood cups I see provide no vibration isolation whatsoever - none (except maybe the psychosomatic acoustical relief they may provide which seems to be directly proportional to their cost). The softer rubber cups would only be effective at high frequencies. Most of the ones I've seen aren't calibrated to the weight of a piano and don't provide the appropriate deflection to even perform well at that. The piano overloads the rubber such that it's essentially a rigid block. The way to vibration isolate a piano is to put it on a raised platform supported on SPRINGS. Only springs have the deflection necessary to isolate low frequencies. How likely is it that one could get a piano owner to build a platform for a vibration isolation problem? Not likely.

With regard to resonant coupling of pianos to stage floors, and whether that affects tone: It depends on whether the piano's on a dolly or not, rubber wheels or nylon wheels, and whether or not the floor is constructed of soft hardwoord, (or hard softwood), or too thick, or too thin, how far apart the joist spacing is, finished, or unfinished, the weight of the pianist, and the type of nails used to secure the floor, or whether Beethoven himself might have once walked across it....I've heard it all. Good luck scientifically determining the factors which affect tone. Tell me what you think you hear. I'll probably just smile and nod knowingly.

Now! Piano techicians. Go! And use your newfound acoustical knowledge for good!

Chris S.

In order to structurally isolate the low frequencies and thereby achieve a reduction in transmitted sound, you will need to achieve 25mm - 50 mm of static deflection from the isolators.