I've seen loose brackets cause some weird noises too, but humming usually points to water pressure issues rather than pipe layout or material. Had a tenant once who swore the pipes were "singing" every night around 10 pm—turned out the city had boosted water pressure at night for maintenance, and his regulator wasn't handling it well. A quick adjustment sorted it out.
Not saying your brackets theory isn't valid, just that humming tends to be more about pressure or valves. Pipe materials can change the pitch or tone, sure, but the actual type of noise—humming vs banging—is usually down to what's happening inside the pipes rather than how they're laid out. I'd double-check the regulator again or maybe look into any recent changes in municipal water pressure.
Yeah, humming usually points to pressure issues—you're spot on there. But I've also seen some weird humming from partially closed valves or even sediment buildup causing turbulence inside the pipes. Had a client once who swore his pipes were haunted because they'd hum randomly during the day. Turned out it was just a gate valve that wasn't fully open, causing water to vibrate as it squeezed past. Quick adjustment and boom, no more ghostly serenades.
Loose brackets or fittings typically give you more of a rattling or knocking sound, especially when water flow starts or stops abruptly. Humming tends to be smoother and steadier, usually tied directly to water flow conditions inside the pipe itself.
I'd definitely check your pressure regulator first, but if that's good, take a quick look at any shutoff valves along the line—sometimes they're not fully open, and that can cause exactly the kind of noise you're describing.
