A pony walks into a bar and asks, "Bartender, may I have a drink?"
The bartender says, "What? I can't hear you. Speak up!"
"May I please have a drink?" asks the pony.
"What? You have to speak up!" the bartender says.
"Could I please have a drink?"
"Now listen, if you don't speak up I won't serve you," the bartender says.
"I'm sorry," the pony adds, "I'm just a little hoarse."
The words horse and hoarse sound exactly the same. They are called homophones. Hoarse means, with a sore throat, so that you can't speak clearly or loudly. You ask someone to speak up, when you can't hear them. It means speak more loudly.