This is my everything and I do mean that. Giving and receiving, these kinds of details are extremely important to me for their ability to sell an extreme size difference. You're never just LOOKING at something that big - everything they do is going to be a noticeable event.
Your examples are perfect. If they speak, it's deep, loud, and rolling. If they're big enough, it might even be a moment or two before the brunt of their voice's volume hits, like crashing thunder. Even breathing can be an event; inhales that accidentally leave a vacuum in front of you for a moment, literally stealing your breath away, and exhales that fill your lungs and bowl you over...
Being subject to the fidgeting and bobbing of a paw beneath a desk, where every repetition is a small series of tremors. The chair above roaring as the owner shifts their weight or crosses their continental thigh.
And, of course, I would be remiss not to mention the vore-related things that set me on fire when I think about them. Being set down on a stomach that's hungry or idly at work. Its growls shake the earth and make you lose your footing, on top of sounding like an actual earthquake. Being near a colossal throat when it swallows, and not just hearing it but -feeling- the sound impact you with such weight and depth that it stuns you for a moment. Being coated in condensation from a half-second of being breathed on during idle conversation with someone; they don't even notice that you're soaked, but you're instantly damp and hot.
Thiiiings of that nature!