The sound was so quiet that I could hardly hear it.

This audio is very clear.

The swing door was opening and closing in the wind.

Please be careful as the platform door is closing.

This train has a selective door operation feature.

He said 'Open Sesame' as if by magic, and the door opened.

He shouted 'open sesame' towards the secret door.

His luck finally turned, and he got his dream job.

Transition metals play an important role in chemical reactions.

Alkali metals are very reactive chemically.