"Hum" Natural Recordings by Native Speakers
Hum is a noun that refers to a low, indistinct sound, often made by an animal, such as a bee or a mouse, or a low, vague noise, such as a distant engine or someone clearing their throat. It can also be used as a verb, meaning to make a low, indistinct sound, or to produce a low, vibrating noise, as in "the engines hummed as the plane took off".
"Hullo" is a casual and informal way of saying "hello". It is an old-fashioned greeting that is no longer commonly used in standard English, but is still found in some dialects, particularly in the UK. It is often used to acknowledge someone's presence or to greet someone in a friendly or informal manner.