amroc - the room mode calculator

Room dimensions:

Modes to display:


Tune of the selected mode:

Shows the tune of the selected mode, just like a guitar tuner. The hand indicates the 'exact' tune in cent (100 cent are 1 half tone).


The so called "Bolt-area" indicates a accumulation of good room ratios. If the red cross lies within this area you have a good chance of more evenly distributed modes.


  • Bolt R.H.: "Spatial Resonance and Standing Wave Patterns in Small Models of Various Shapes", JASA 10 (1939)
  • Bolt R.H.: "Frequency Distribution of Eigentones in a Three-Dimensional Continuum", JASA 10 (1939)
  • Bolt R.H.: "Normal Modes of Vibration in Room Acoustics: Angular Distribution Theory", JASA 11 (1939)
  • Bolt R.H.: "Angular Distribution of Normal Modes", JASA 11 (1939)

Bonello (modes per third):

Shows the number of modes per third up to your chosen limit-frequency, beginning with the lowest mode. According to the "Bonello-criteria" this function should be strictly increasing to reach a good distribution of modes.


  • Bonello, Oscar J.: "A New Criterion for the Distribution of Normal Room Modes" - AES-Journal(USA) 29 (1981)\n\n\
  • Bonello, Oscar J.: "Acoustical evaluation and control of normal room modes" - JASA 66 (1979)

Room 3D

Displays the room in 3D. Select a mode above to see its pressure zones.

Additional data about the room:



RT60: sec


Critical distance:

Equivalent absorption area needed:
Average absorption coefficient needed:
Hi :) Calculation time warning! close

You can

  • start the calculation anyway
  • close this dialog and change your
    • room dimension
    • reverberation time
    • lower/upper limit frequency for calculation

Planung und Bau eines schallisolierten Proberaums