What are causing the sounds from barbecue hotplates when they first heated or cool down?

The sounds you hear from barbecue hotplates when they are first heated or cooled down are caused by the expansion and contraction of the metal. As the hotplate heats up, the metal expands and this causes the hotplate to vibrate, producing a crackling or popping sound. When the hotplate cools down, the metal contracts and this also causes the hotplate to vibrate, producing a similar crackling or popping sound.

The rate at which the hotplate heats up or cools down can affect the pitch of the sound that is produced. A hotplate that is heating up quickly will produce a higher-pitched sound than a hotplate that is heating up slowly. Similarly, a hotplate that is cooling down quickly will produce a higher-pitched sound than a hotplate that is cooling down slowly.

The type of metal that the hotplate is made of can also affect the sound that is produced. Hotplates made of different metals will vibrate at different frequencies, producing different sounds.

In addition to the expansion and contraction of the metal, the presence of food or grease on the hotplate can also affect the sound that is produced. Food or grease can cause the hotplate to vibrate differently, producing a different sound.

The sounds that you hear from barbecue hotplates when they are first heated or cooled down are a normal part of the operation of the hotplate. These sounds are not a cause for concern.