Sound Check: The Science You're Already Ignoring

You walk your stores. You check the fixtures, the lighting, the signage, the staffing levels. You look at the traffic counter on the way out. You probably glance at the playlist, if you notice it at all, and move on.

Meanwhile, a body of peer-reviewed field research dating back more than forty years has been measuring what that music does to your customers. The studies run across supermarkets, restaurants, wine shops, and flower stores in multiple countries. The findings are specific, the effects are measurable, and almost none of it has made its way into how most operators actually choose what plays in their stores.

In 1982, Ronald Milliman published a field experiment in the Journal of Marketing. He alternated between slow-tempo and fast-tempo background music in a supermarket and tracked what happened. Shoppers moved through the store more slowly when the tempo dropped. That part is intuitive. The part that matters for your P&L: daily sales volume was 38.2% higher on slow-tempo days.

Customers didn’t report noticing the music at all. When asked, they had no awareness that the tempo had changed.

Four years later, Milliman replicated the finding in a restaurant. Slow background music caused diners to stay longer at the table. They didn’t eat more food, but they ordered significantly more drinks. The tab went up because people lingered. Caldwell and Hibbert confirmed the same pattern in 1999.

The mechanism is straightforward. Slower music slows the pace of the environment. People take more time, handle more merchandise, and buy more. The 38.2% number comes from one study in one supermarket, and replication strength varies. But the direction has been consistent for four decades.

Tempo alone turned out to be an incomplete picture. Knoferle and colleagues ran a field experiment, published in 2011, testing tempo alongside musical key. They found an interaction effect. Slow tempo in a minor key produced significantly higher sales. Slow tempo in a major key did not. The original Milliman finding essentially disappeared when the music was bright and upbeat.

A retailer who reads the Milliman study and fills their playlist with slow, cheerful pop has probably undone the effect they were going for.

Most playlists are assembled without any awareness that key signature matters at all. Nobody checks. Nobody measures.

Areni and Kim published a study in 1993 looking at a wine store. When classical music was playing, customers purchased more expensive wines. The music didn’t make them like wine more. It shifted which wines felt like the right choice in that room. The genre signaled a price bracket, and customers bought accordingly.

Gueguen and Jacob ran a similar study in a flower shop, published in 2013. When romantic music was playing, average customer spending jumped from EUR 25.31 to EUR 32.55. The genre matched the product category and the purchase occasion.

Mattila and Wirtz added another dimension in 2001. When the arousing qualities of ambient scent and background music matched each other, store evaluations improved significantly. When the match broke, evaluations dropped. The entire sensory environment needs to tell a coherent story, or customers notice the friction even if they can’t name it.

Smith and Curnow published a study in 1966, over sixty years ago, showing that shoppers spend significantly less time in a store when music is played at high volume. Louder music compresses dwell time. Shorter visits mean fewer purchases.

The finding has held up. And yet most retail environments have no volume protocol. No target decibel level. No variation by time of day. The volume is set by whoever opens the store, and it stays there. During a quiet Tuesday morning and a packed Saturday afternoon, the same volume hits the room very differently. A fixed volume setting means the actual perceived loudness changes with foot traffic, HVAC noise, and conversation density. Nobody is adjusting for it.

The typical approach to retail music is to pick a genre or mood that feels approximately right and let a streaming platform handle the rest. Nobody is checking the key signature distribution of the playlist. Nobody is running a volume protocol tied to occupancy. The research exists. Researchers have replicated these findings across decades, countries, and retail categories.

The gap between what’s been studied and what’s been applied is forty years wide. Operators who manage every other variable in their stores, from lighting color temperature to fixture height to staff scheduling, are leaving music entirely unmanaged.

That gap is also an opportunity. If you run multiple locations, even a small, controlled change to your audio environment gives you something to measure against your existing traffic and sales data. Walk your stores this week. Listen. Ask yourself whether what you hear was chosen with the same intention as what you see.

This is part of the Sound Check series. The rest of the series sits on the why page.