Shure A15HP In-Line XLR Barrel 100 Hz High Pass FilterThe Shure A15HP filter rolls off low audio frequencies to reduce 60 Hz electrical hum, low frequency wind noise, air conditioner noise, or stand and floor transmitted low frequency vibrations. Features : When loaded with a low impedance microphone input (800 ohms or more), the rolloff is 12 decibels per octave below 100 Hz. When loaded with 150 ohms, the rolloff is 3 decibels at 100 Hz. The output is flat above the rolloff point (with a maximum loss