What do molecules sound like? In chemistry, we rarely take advantage of the full panoply of senses available to most humans. Although, as Phillip Ball wrote in January this year that ‘chemistry is the most sensuous science … vision, taste and smell have always been among the chemist’s key analytical tools’, we now sensibly avoid using one of these (molecular gastronomists aside, I’m not aware of a lab that encourages tasting of samples) and rarely, if ever, take advantage of our other senses: touch and hearing.

For researcher David Watts, the idea of listening to organic molecules had been ‘languishing in a notebook’ since he first visualised compounds as tiny stringed instruments. As each molecule has a vibrational signature, it should be possible to convert them to characteristic musical tones. David realised that data from Fourier transform infrared spectroscopy (FTIR) should provide all the necessary information, ‘the frequency and amplitude of absorption in the bonds’, albeit in the wrong format for direct conversion to sound. He designed a second step to create audible sound waves from those vibrations. ‘If an inverse Fourier transform is performed then the FTIR spectrum can be converted into the time/amplitude domain and the vibrations of the molecules heard.’

You can hear his results online at The sounds of chemical molecules. The sounds themselves vary between a telephone tone and the sort of discordant sounds used to create tension in budget science fiction, but making beautiful music was never the aim. This was part curiosity and part proof of principle, but Watts can already see a number of applications.

‘Having the sound of a molecule allows you to perceive it using our auditory sense,’ he told Chemistry World. ‘This alone in my view justifies the experiment.’ Most people, except perhaps those with perfect pitch, would not be able to discern structural/functional information from a static tone, but Watts argues that this isn’t the point – sound adds an additional element to a researcher’s relationship with molecules. ‘Maybe this auditory chemical perception ability can be learnt with practice and be useful for organic chemists as an additional way for them to connect or understand their molecules. A particularly interesting idea is in the auditory monitoring of a chemical reaction, maybe an online FTIR monitoring system could provide reaction progress feedback or offer insight into reactions and their intermediate states. The use of the extra sense of hearing allows you to watch and perform an experiment whilst listening to its progress.’

Giving a voice to a molecule is fairly straightforward. ‘Sounds can be created for any molecule providing a digital spectrum is available,’ says Watts. Although the exact applications are still unclear, it may be wise to start compiling the music of the molecules now, so that we’re ready when those uses do become apparent. ‘In my opinion, the auditory representation of the molecule should be obtained for all molecules and included in online databases as extra information for familiarization purposes and potential future uses,’ says Watts.

As a proof of concept, Watts’ demo proves that accessing an additional sense is well within the realms of possibility. The sine waves he generates may be somewhat grating, and I’m not sure I could bring myself to listen to them throughout the process of a reaction, but they’re just a first step. Next would be to find a waveform that is more pleasing to the ear, or modulate it with additional data. Perhaps temperature could set a rhythm, syncopated by pressure. Soon, we could all be dancing to a molecular melody.

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