Enter the degree of directivity and the equivalent absorption surface into the Calculator. The calculator will evaluate the Critical Distance. 

Critical Distance Formula

dc=.25 * SQRT(y*A/pi)


  • dc is the Critical Distance ()
  • y is the degree of directivity
  • A is the equivalent absorption surface

To calculate the Critical Distance, multiply the degree of directivity by the equivalent absorption surface, divide by pi, take the square root of that result, then multiply by .25.

How to Calculate Critical Distance?

The following steps outline how to calculate the Critical Distance.

  1. First, determine the degree of directivity. 
  2. Next, determine the equivalent absorption surface. 
  3. Next, gather the formula from above = .25 * SQRT(y*A/pi).
  4. Finally, calculate the Critical Distance.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

degree of directivity = 41

equivalent absorption surface = 123