Other ambient noise - a rushing sound reminiscent of ocean surf - also persisted.

Finally they settled down, and only their vocal noises persisted.

After a little while, much of the racket went away, though a more muted rumble and several medium-loud mechanical noises persisted.

The noise persists.

Like the alarm of an unbelled clock, the noise persisted from the living room, coming above the rumble of the steamship's engines.

Try reducing this slightly, and call an expert in if the noise persists.

The noise persisted and intensified.

The noises persisted, and I called upstairs to ask if there was anything we could do.

The noise persisted, low but troubling.

Call an expert in if the noise persists.