The Conceptual Design of High Pressure Reversible Axial Tunnel Ventilation Fans

Table 4

System acoustic calculation at the tunnel and atmospheric side.

		63 Hz	125 Hz	250 Hz	500 Hz	1 KHz	2 KHz	4 KHz	8 KHz
Tunnel side
Fan LW		123	120	130	130	127	121	120	114
System losses		0	0	0	0	0	0	0	0
Room effect		−3	−5	−7	−9	−10	−11	−11	−12
Attenuator insertion loss		−16	−32	−45	−50	−50	−50	−38	−27
Resultant LwA (85 dBA spec)	81	104	83	78	71	67	60	71	75
Atmospheric side
Fan LW		123	120	130	130	127	121	120	114
System losses		−2	−3	−4	−5	−5	−5	−6	−6
Atmos effect		−14	−14	−14	−13	−13	−13	−13	−13
Attenuator insertion loss		−8	−20	−33	−40	−50	−48	−25	−15
Resultant (85 dBA spec)	82.3	99	83	79	72	59	55	76	80