A loud-hailer, also known as a megaphone, is a device used to amplify sound and make it louder and clearer. However, there are several other words that can be used instead of loud-hailer, such as bullhorn, hailer, trumpet, and speaking-trumpet. Bullhorn is perfect for use in sports events and protests, while a hailer is suitable for use in maritime settings. Trumpet is suitable for use in orchestras and military bands, while a speaking-trumpet is perfect for use in old naval ships. These synonyms can be used interchangeably depending on the context and the desired effect.