Combination tone

Abstract: Subjects made same/different judgments concerning the pitches of two successive tones In Experiment 1, the two tones were played on either the same instrument (guitar, flute, trumpet) or on different instruments In Experiment 2, the first tone was always a sine wave and the second was one of the same three instrumental tones Following the sine wave, but before presentation of the second tone, people were asked to form an image of what an assigned instrument would have sounded like playing that pitch A match between this imagined timbre of the first tone and the timbre of the second tone produced faster reaction times to identical pitches than a mismatch

Abstract: Like our other senses, the auditory system can produce illusions. Prominent among these are distortion products: when listening to two tones, one of frequency f1 and the second of a higher frequency f2, an individual may hear not only these primary tones, but also a difference tone of frequency f2 - f1, a sum tone of frequency f2 + f1, and combination tones of frequencies such as 2f1 - f2 and 2f2 - f1. Discovered by Tartini early in the eighteenth century, these illusory sounds are sufficiently conspicuous that they were employed to carry melodies in classical compositions. Distortion products originate within the cochlea, where they manifest themselves in the basilar membrane's vibration. Here we demonstrate distortion products in individual hair cells of the bullfrog's sacculus, where they emerge from a nonlinearity inherent in the mechanoelectrical transduction process. In addition to offering an explanation for cochlear distortion products, our results suggest that the mechanical properties of hair bundles significantly influence the basilar membrane's motion.

Abstract: 1. In the cricket,Teleogryllus oceanicns, an identified auditory interneuron, interneuron-1 (int-1), is described morphologically and physiologically (Figs. 1,2). There is one such neuron in each hemiganglion of the prothoracic ganglion. The medial dendrites of int-1 overlap part of the terminal field formed by the auditory afferent axons from the ear and int-1's axon ascends to the brain, terminating on the same (ipsilateral) side (Fig- 2). 2. The neuron has a two-part frequency response characteristic: (1) its spontaneous activity is suppressed by low frequencies (3 to 8 kHz) at threshold-to-moderate intensities (Fig. 9 B), and (2) it is strongly excited at high frequencies, especially ultrasonic, from 15–100 kHz (Fig. 3). 3. Int-1 produces more spikes per tone pulse (Fig. 4) and its reponse latency decreases (Fig. 5), with increasing levels of intensity when stimulated by ultrasound. 4. Two-tone inhibition occurs in int-1. When a 30 kHz (normally excitatory) tone is combined with a 5 kHz tone (which suppresses spontaneous activity), the combination tone results in a diminished response, compared to the response to the excitatory tone alone (Fig. 6). 5. The excitation of int-1 shows lateralization. Excitation is stronger in the neuron ipsilateral to the sound source, than in the contralateral int-1 (Fig. 9). 6. Int-1 responds to electronically-generated pulse trains that simulate bat-echolocation signals. The neuron is responsive to a range of ultrasonic frequencies that are contained in the echolocation signals of insectivorous bats (Fig. 11). 7. In light of its response characteristics, we speculate that int-1 plays a role in the detection of ultrasonic signals emitted in the cricket's normal environment by hunting bats.