Why is the term Roger Wilco considered by some to be an incorrect phrase - trivia question /questions answer / answers
Aerophones; any class of musical instruments in which a vibrating mass of air produces the initial sound including bull roarers and sirens. They are found in many countries throughout Africa and are normally incorporated with dancing, the musicians having to synchronize their footwork along with playing their notes!
The term Assistive Listening Systems (ALS) is a generic description of several different technologies that essentially do the same thing: they are used to improve the reception of speech for people with hearing loss in situations when it might be difficult or impossible to hear otherwise.