Researchers have discovered what they described as the olfactory equivalent of white noise, stemming from a combination of several compounds.
The scientists, who reported the finding in the Proceedings of the National Academy of Sciences, said it is best for one to go to a laboratory and personally experience it.
"The best way to appreciate the qualities of olfactory white is to smell it," the researchers wrote, according to LiveScience.com.
'Bland beyond description'
According to them, "olfactory white" is a mixture of different compounds, just as white noise is a mix of frequencies and white light is a mix of many wavelengths.
LiveScience.com added the scent is "so bland as to defy description," with participants in an experiment rating it in the middle of the scale for pleasantness and edibility.
In their report, the researchers found that the more components there were in each of two mixtures, "the more similar the smell of those two mixtures became, even though the mixtures had no components in common."
LiveScience.com said neurobiologist Noam Sobel from the Weizmann Institute of Science in Israel and his colleagues did the study to find out if the "white" phenomena with light and sound could also apply to smelling.
In their experiments, the researchers exposed participants to hundreds of equally mixed smells, between one and up to 43 components.
An initial 56 participants were made to compare mixtures of the same number of compounds with one another.
"For example, a person might compare a 40-compound mixture with a 40-compound mixture, neither of which had any components in common," LiveScience.com said.
The experiment showed that the more components in a mixture, the worse participants were at telling them apart.
LiveScience.com said a four-component mixture smells less similar to other four-component mixtures than a 43-component mixture smells to other 43-component mixtures.
Finding olfactory white
The researchers set up a new experiment where they first created four 40-component mixtures.
In this experiment, 12 participants were given one of the mixtures to sniff and told that it was called "Laurax," a made-up word.
Three of the participants were told compound 1 was Laurax, three were told it was compound 2, three were told it was compound 3, and the rest were told it was compound 4.
After three days, the participants were given four new scents and four scent labels, one of which was Laurax. They were then asked to label each scent.
The researchers found the label "Laurax" was most popular for scents with more compounds.
"In fact, the more compounds in a mixture, the more likely participants were to call it Laurax. The label went to mixtures with more than 40 compounds 57.1 percent of the time," it said.
A second experiment similar to the first let participants label one of the scents "other," to ensure "Laurax" was not just a catch-all.
This time, scents with more compounds were again more likely to get the Laurax label.
The researchers said the result showed olfactory white is a distinct smell, caused not by specific compounds but by certain mixes of compounds.
But they said the key is that the compounds are all of equal intensity and that they span the full range of human smells.
"In other words, our brains treat smells as a single unit, not as a mixture of compounds to break down, analyze and put back together again. If they didn't, they'd never see mixtures of completely different compounds as smelling the same," LiveScience.com said. — TJD, GMA News