Remove hissing sound from mic

Hi, I bought a pair of Behringer C-2 microphones. I plugged them into my mixer (MC6002S), and they both work. The only issue is a harsh hissing sound every time I record audio. Do you have any ideas?

Software audio processing is my first guess at a solution. A noise gate and ‘de-esser’ filter would help reduce any low-level hissing. I feel like you’ll get better advice if you find an audio tech sub. Troubleshooting vague audio issues can be a lengthy and frustrating rabbit hole, haha. You might be looking for a ‘low pass filter’ or something to target the noise frequency.

I accidentally found out that my PC has a terrible sound card built in. I’ll just purchase an audio interface and sell the mixer.