The sound of science: using acoustics for coffee roasting

An underwater acoustician has used his skills for quite a different purpose: developing an automated system for roasting coffee beans. Preston S Wilson explored the potential of using the ‘cracking’ sounds emitted by coffee beans during the roasting process as the basis for an automated acoustical roast monitoring technique.

This is believed to be the first quantitative assessment of these sounds and the first suggestion to use them in an automated control process.

In the Journal of the Acoustical Society of America, Wilson describes how he found three parameters of the crack sound that he says could be used. Towards the end of the roasting process, sounds known as ‘first crack’ exhibit higher acoustic amplitudes than the ‘second crack’ sounds that are emitted later. Finally, the rate of cracks in the second crack chorus is higher than the rate in the first crack chorus.

“The sound of the first crack is similar to popcorn popping, while the second crack is more akin to the sound of the breakfast cereal Rice Krispies,” said Wilson.

An automated acoustical roast monitoring technique “could lead to optimised coffee roasting, which would increase quality, decrease errors in roasting and potentially save energy used to power the roasting process”, he said.

Initially, Wilson’s project was unfunded and conducted out of personal interest, but he says a commercial application may emerge for the coffee roasting industry.

Wilson says that taking it to the next level and commercialising the process will “require quite a bit of effort - engineering the design of the sensor system, the data acquisition and processing. It will require writing software to automatically process the sounds, and then integrating it into the control system.”

The article ‘Coffee roasting acoustics’ by Preston S Wilson appears in the Journal of the Acoustical Society of America - Express Letters.