Can’t remember where you left your cellphone? Totally forgot about that dentist appointment? If you’re past middle age and really want to hang on to your memory, swap the Sudoku and crossword puzzles for a good night’s sleep.

Many studies have made the connection between sleep and memory consolidation—the brain’s ability to cement short-term memories into longer-term ones, so they can be recalled the next day. But as we age, deep, refreshing slumber can be as elusive as those misplaced car keys.

Thus, an experimental technology that enhances sleep, according to the Northwestern University scientists who developed it, could present a breakthrough for older people suffering memory loss. In a series of tests, researchers at Northwestern found that when “pink noise”— an engineered sound that scientists say is more soothing than the better-known white noise — was delivered in short bursts during sleep, older people showed better cognitive function after waking than they did after a night without pink noise.

Pink noise, which is a composite of sounds, differs from white noise because each of its individual sounds carries the same frequency, unlike notes in music, say, whose frequencies double with each higher octave. In short, the frequencies are more balanced than white noise.

“This is a simple, safe, non-pharmacological approach” to improving one’s memory, says Phyllis Zee, a professor of neurology at the Feinberg School of Medicine at Northwestern and senior author of the study, published recently in the journal Frontiers in Human Neuroscience. What the study showed, she and her co-authors say, is that acoustics can be used to enhance the quality of older people’s sleep, and can improve their memory in the bargain.

Earlier research by Jan Born and colleagues at the University of Lubeck in Germany found a link between acoustic stimulation and deep sleep (also known as slow-wave sleep) in young adults. His group found that subjecting the sleepers to pink noise enhanced slow-wave brain activity.

But until now, such studies in the elderly population — the group with the most difficulty getting sleep, and thus at highest risk for memory impairment — have been lacking, Zee says.

In the Northwestern study, 13 healthy men and women between 60 and 84 were monitored as they slept on two nights about one week apart. Each person was subjected to pink noise on just one of those nights, though they were not aware of this, as a control. The sample size was “relatively small,” due to the unusual demands placed on the subjects’ time, but this didn’t bias the results, Zee says, because each person experienced both the actual stimulation and a night of no noise, thus reducing the variables involved.

While the subjects slept, their brain waves were monitored using electroencephalography, which recorded their neural activity and sent the information to a computer. The pink-noise bursts were played through headphones at specific intervals, synchronized according to each subject’s brain waves.

To measure the acoustic stimulation’s effect on memory, the participants were tested on 88 word pairs before they went to sleep, and again in the morning. On average, word recall following the nights of pink noise was about three times as great as it was after the noiseless nights.

“The advantage of our algorithm is that it’s individualized and automatic, adjusting to each person’s sound-wave sleep, which can differ from night to night,” says Roneil Malkani, an assistant professor of neurology at Northwestern and a co-investigator. “The timing is important to get the most beneficial effect.”

Robert Stickgold, associate professor of psychiatry at Harvard Medical School, who wasn’t involved in the Northwestern research, calls the results “very impressive.” But questions remain about whether such an intervention would keep us mentally nimble, says Stickgold, who is also director of the Center for Sleep and Cognition at Beth Israel Deaconess Medical Center in Boston.

“Sleep enhances other kind of memories as well—like emotional memories,” he says. “My concern is by concentrating only on this one kind of memory, we could be potentially impairing other types of memory where research has not been done and where there is no data.”

The Northwestern researchers are doing more testing in young and older adults to see how acoustic stimulation might perform over a longer period, including one study in patients with mild cognitive impairment, sponsored by the National Institutes of Health, Alzheimer’s Association and Illinois Department of Public Health. A patent is pending for the pink-noise algorithm, and the researchers plan on developing devices for home use in the near future.