Why the new Dutch heat pump is so quiet: “One of us was playing the trumpet”

The Whspr is a heat pump so quiet that it can be placed right up against the property line. But how did the manufacturers manage to make it so quiet? “We’re completely obsessed with heat pumps.”

Hugo Huis in ‘t Veld and Hans Cool worked at Eneco. “There, we encountered the problem that heat pumps were too loud for townhouses. So we set out to find a solution,” says Cool.

Horizontal fan

“Most of the noise is caused by air being forced through the grille,” Huis in ‘t Veld continues. “But if you remove that grille, it’s not safe. The grille also has to be quite fine-meshed, because fingers mustn’t be able to reach the fan—there are very clear rules about that. Then I realized the air could go through a pipe that you can’t stick your hand into.”

To develop this idea further, the two teamed up with TNO and a party that prefers to remain anonymous, but which has a great deal of expertise in airflow. “We took advantage of that,” says Cool. “In a brainstorming session with them, we realized that the fan had to be positioned horizontally.”

Unobstructed in every way

Huis in ‘t Veld: “One of the people in that brainstorming session played the trumpet. They use a cone to muffle the sound, and we immediately applied that same principle to the heat pump.” That cone is located right below the fan, where the sound is muffled immediately. “We were also able to fit the compressor inside that cone, and that space is well insulated, which further dampens the sound.”

Cool: “The air then flows out through four large openings and isn’t obstructed anywhere. That’s why you hardly hear it at all.”

Standard heat pump

“The great thing is that we’re not experts on heat pumps at all. Although we do know how they work, of course—we’re both engineers,” says Huis in ‘t Veld. “I even took one apart completely once.”

Cool adds: “As far as the refrigeration technology is concerned, there’s nothing special about it—we left that alone. We use the same well-established technology as any other heat pump. But that flow is unique, and in terms of installability, we’ve done some innovative things—we hold several patents on those.”

Innovation is that simple

It seems so simple: place the fan horizontally and leave out the grilles. Still, you have to think of it first. “People told us: ‘That heat pump is fully developed—what more can you possibly add to it?’” says Huis in ‘t Veld. “But sometimes you have to look at something from the outside to see what can be improved. Take suitcases, for example. Until the 1970s, people dragged them to Schiphol Airport. Then someone came along and put wheels on them. Innovation can be that simple.”