Possible Clues:

• At greater volume
• Noisier
• At higher volume
• 'Behold, it gets rude - even more, by the sound of it (6)'
• 'Do with a rule to get more, by the sound of it (6)'
• 'Speak up!'
• At a higher volume
• 'I can't hear you!'
• More noisy
• With greater volume