<Tr> <Th> Sound exposure </Th> <Td> E, SEL </Td> </Tr> <Tr> <Th> Acoustic impedance </Th> <Td> Z </Td> </Tr> <Tr> <Th> Speed of sound </Th> <Td> </Td> </Tr> <Tr> <Th> Audio frequency </Th> <Td> AF </Td> </Tr>

Which of these factors will increase the speed of a sound wave in air