All at once, he heard a gentle whirring somewhere amongst the toys.

All at once he heard a gentle whirring somewhere amongst them.

There was a gentle whirring, and on the screen appeared hundreds of strange beings moving rather jerkily to and fro.

While he was thinking it over, he became aware of a gentle whirring sound coming from the top of the stairs.

There was a heartbeat's delay, and then the air filled with gentle whirring sounds as the arrows came down to earth.