U-Mix 44 High Pitched Noise

Hello
I have a U-Mix 44 and I get a high pitched crackling noise over my monitor speakers when it is plugged into my computer.
I have tried using different cables but it still happens.
Please can you help!
Thanks
James
I have a U-Mix 44 and I get a high pitched crackling noise over my monitor speakers when it is plugged into my computer.
I have tried using different cables but it still happens.
Please can you help!
Thanks
James