What is "acoustic figures"

Sonorous \So*no"rous\, a. [L. sonorus, fr. sonor, -oris, a sound, akin to sonus a sound. See Sound.]

1. Giving sound when struck; resonant; as, sonorous metals.

2. Loud-sounding; giving a clear or loud sound; as, a sonorous voice.

3. Yielding sound; characterized by sound; vocal; sonant; as, the vowels are sonorous.

4. Impressive in sound; high-sounding.

   The Italian opera, amidst all the meanness and familiarty of the thoughts, has something beautiful and sonorous in the expression.
   --Addison.

   There is nothing of the artificial Johnsonian balance in his style. It is as often marked by a pregnant brevity as by a sonorous amplitude.
   --E. Everett.

5. (Med.) Sonant; vibrant; hence, of sounds produced in a cavity, deep-toned; as, sonorous rhonchi.

   Sonorous figures (Physics), figures formed by the vibrations of a substance capable of emitting a musical tone, as when the bow of a violin is drawn along the edge of a piece of glass or metal on which sand is strewed, and the sand arranges itself in figures according to the musical tone. Called also acoustic figures.

   Sonorous tumor (Med.), a tumor which emits a clear, resonant sound on percussion. [1913 Webster] -- So*no"rous*ly, adv. -- So*no"rous*ness, n.