Howler Monkey

The loudest animal in the world is the blue whale: its vocalisations of up to 188 decibels can be heard 160km away. But as it's also the largest animal, that's only 0.0012dB per kilo of body mass. The loudest land animal is the howler monkey at 88dB, which emits an impressive 11dB per kilo - almost 10,000 times louder per unit mass. But the pistol shrimp leaves them both cold. Although the sound is much higher frequency and travels only a few centimetres, the snap from its claws can register 190dB. Since the shrimp itself weighs just 50g or so, this works out at a hugely disproportionate 3800dB per kg.