Keening

The keening whistle of the teapot signaled that the water was boiling.

The keening screech of the brakes startled the pedestrians on the sidewalk.

The keening of the steam whistle signaled the departure of the train from the platform.

The keening smell of rotten eggs filled the kitchen, indicating a gas leak.

The traveler explored foreign lands with a keening spirit, constantly seeking new experiences.