﻿ Calculation of Required number of punched hole in resonator type muffler

# Calculation of Required number of punched hole in resonator type muffler

 1 Inside diameter of duct：D (mm) 0＜D 2 Octave band center frequency：fr (Hz) =Resonant frequency. 0＜fr. 3 Target attenuation value：R (dB) 0＜R 4 Diameter of punched hole：d (mm) 0＜d 5 Thickness of duct：l (mm) 0＜l 6 Sound velocity：v (m/s) 0＜v 7 Graph x：fr(Hz),y：Required number of punched hole x：R(dB),y：Required number of punched hole x：K,y：Octave band attenuation value(dB) Plot Input Data： YesNo 8 Number of gridlines of Graph x-axis, y-axis Figure： OnOff
:Export Graph Image.

## Keyword

Required number of punched hole,resonator type muffler,Inside diameter of duct,Octave band center frequency,Resonant frequency,Target attenuation value,Diameter of punched hole,Thickness of duct,Sound velocity

## Reference

[1]：前川純一：『建築・環境音響学』,共立出版,1990,pp.121-127.

## Remarks

・Conductivity of one hole：G(mm)
・Area of one hole：s(mm^2)
・Volume of airtight hollow：V(mm^3)
・Required number of punched hole：N
・Cross section of duct：S(mm^2)
・Wavelength of resonant frequency：λr(mm)=v/fr*1000