Indeed, battery failure can lead to diminished sound output in your AirPods. When your AirPods' battery life has significantly decreased, the sound may become quieter than expected. This occurs because the speakers responsible for generating sound in your AirPods rely on the battery for power. A weak battery is unable to provide the necessary energy to the speakers, causing reduced sound levels. If you consistently encounter this problem, it's advisable to have your AirPods' battery replaced. Visit an authorized Apple store or a certified repair center for the battery replacement service.