Acoustics First BLOG

After being outside on a hot summer’s day, nothing quite hits the spot like a slice of a cool, crisp, sweet watermelon. Unfortunately, not every watermelon is the same, and everyone has different methods for selecting the best ones.

There are number of visual clues that one can rely on to help identify a good watermelon. A large, yellow field spot on the bottom indicates that the watermelon was on the vine longer and is probably sweeter. Also, the coloring of a “ripe” melon will have strong, consistent stripe pattern; dull dark green stripes alternating with light yellow/pale stripes.

However, even when I followed these visual tells, I would often cut into my purchase only to be dismayed by a Styrofoam-like, flavorless inside or an over-ripened, mushy mess.

This melon melancholy haunted me until a few years back when I saw a middle-aged woman kneeling on the concrete floor of the supermarket with 5 watermelons circling her. I watched as she bent over and carefully knocked on each one, listening and nodding her head like she was holding a séance with the “other side” of the produce aisle. She repeated this process, rearranging the melons in front of her, until she picked up “the one” and put it in her cart, returning the other watermelons to the display bin.

I greeted the woman, trying not to startle her, and admitted that I often struggled to pick out watermelons. Clearly, she knew what she was doing and I was curious if she might share her system with me.

She kindly told me that she was listening for a “hollow” sound, that was full, but not too deep in pitch. I told her that I had heard that this “knock” test is a good way to judge the water content, but I never had much luck. She said that people will make the mistake of holding onto the melon when knocking, which quickly dampens the sound, so you can’t hear much of a tonal difference between melons (like palming the string of a guitar will change its sound to a shorter, more percussive, note).

Her strategy is to pick out 4-6 similar sized melons that have a large, yellowish sugar spot and strong striping, then sets each down so the only point of contact is with the hard floor. Without external dampeners, the melon can really “sing” when knocked, telling her how far along the fruit is. Too deep of a sound and the fruit is over-ripe/mushy, too high-pitch (or not hollow at all) and the watermelon is not ripe enough. She organizes the melons from lowest to highest in pitch and she simply selects from the middle melons to find one or two that are “just right”.

She said that this ritual, as ridiculous as it might appear to other shoppers, is the best way to guarantee a good watermelon and it’s worked for me ever since; so, don’t knock the knock!