292 Are the Androids Dreaming Yet? clever mathematics to generate speech from seed information. For a given speaker the vowel ‘a might be 20% middle C, 50% F and 25% A, with a few other things thrown in for good measure. We can transmit this information and ask the computer at the other end to re-synthesize it. This is what happens when you listen to someone on a modern phone. You do not hear their actual speech, you listen to a computer synthesizer make a near approximation. CD is no longer the gold standard for sound. Professional audio has standardized on 24 bit recording which is probably far beyond the limit of the human ear. An audio soundtrack is doing a good job at 2 million bits per second. Sitting perfectly still in the middle of a room, each ear will pick up a different signal if the source is not directly in front of us. The two ears on a human head face a little forward, and the hair on your head slightly absorbs sound. We can calculate the source of the sound by the slight difference in the times at which it strikes each ear, and the variation in frequency content. We can use these two pieces of information to determine the direction from which a sound is coming. It was useful for our ancestors to be able to tell where the saber-tooth tiger was hiding. We can gain more accurate information by turning our heads from side to side. The differences in frequency and timing should vary as we do so and we gain a little more data to perform the calculation. If we walk through the room we sample yet more of the soundscape and this can be used to pinpoint the exact location of the source. As we move, we expect the sounds we hear to change subtly according to the mental model we use for locating objects in the soundscape. To give the illusion of a soundscape modern systems use multiple microphones to capture the sound, so it can be reproduced on multiple speakers. Ideally, we would record a hologram of the sound but it is possible to record on thirty or so mi