Room dimensions:

Modes to display:


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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).

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)
  • 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.

In these areas the mode will be loudest, best to absorb and if the sub is inside such an area the mode will be most excited. So try to move your sub or your listening position out of those areas if you have a strong mode!

Red and blue means the same (maximum pressure). It is just easier to recognize the different zones at higher order modes with those two highly different colors.


The bolt area was a nice way to find room ratios when computers were not widely available. Richard Henry Bolt created this diagram to indicate an accumulation of good room ratios. Instead of calculating each mode (by hand) to see the mode distribution, one could look at that diagram, increasing the chance of being near a good distribution.

amroc calculates and visualizes each mode in no time. So finding better room ratios and understanding their mode distribution have become much more accessible. I leave this diagram in here as it has excellent historical relevance, but I recommend not taking that shortcut and enjoying the possibilities of the computer age :) Sure, it can be overwhelming at the beginning to dive deep, but hey...there is help :)


  • Bolt R.H.: "Angular Distribution of Normal Modes", JASA 11 (1939)

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

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