This is a really weird problem. When my MBP has sustained network utilization roughly >5Mbps, it makes a faint high pitched whine. It's not the fans, and it's more pronounced when using ethernet but does occur on wireless as well. Is this normal? I've had two MacBooks prior to this and neither of them made this noise. P.S., It isn't a HDD sound as I have an SSD. Speakers are muted, and no other devices connected.