But these were by major themes against the continuous hum and buzz of the city.

His ears were becoming blocked from the continuous steady hum of engines.

He scanned the enclosure from behind his goggles, listening to the continuous hum of working machinery.

The wood was filled with people, and a continuous hum of voices rose up under the tangled foliage of the tall trees.

The village was quiet, save for the continuous hum of the electric generator.

A faint and continuous hum of mechanism came from the case.

Now its absence was noticeable and it produced the same sensation within Morrison as the sudden cessation of a continuous low hum would have.

In the school the clamor of 1,400 student voices meshes into a continuous hum.

Imagine, first, a horseshoe bat giving out a continuous hum of ultrasound as it flies fast towards a still object, like a tree.

Before he could respond, the phone made a loud click, and then a continuous hum.