Japanese toy maker Takara Tomy Arts, Honda, and the Tokyo-based Society for Harmonic Science (also known as the Sound Healing Society) have developed the Baby Smile Honda Sound Sitter. From the outside, it looks like a 1960s S600 Coupe, but there’s a secret inside in the form of a sound unit that plays actual engine sounds recorded from the second-generation NSX.

According to Honda, this collaboration came out of research they’ve done as to why babies often drift off to sleep whenever you put them in a car seat and go for a drive. One explanation they found, while working with the Society for Harmonic Science, is that to a baby’s ears, the sounds of a car engine are like the sounds they heard inside their mother’s womb.

From there, the Society for Harmonic Science examined roughly 30 different Honda engines, analyzing their frequencies to see which most resembled the sounds heard in the womb. While you might expect a sensible family sedan to be the closest proximity, the researchers instead found that the second-generation NSX, Honda’s high-performance, mid-engine sports car (specifically the 2018 model) is the most womb-like.

When the front of the plushie is pressed, the sounds of the NSX revving play for 45 seconds (but a second press will quiet it sooner). Initially, the designers considered fitting the plushie with some sort of external speaker to make the sound more noticeable. Ultimately, though, they opted for an internal unit, to replicate the acoustics of an engine more closely.

The Baby Smile Honda Sound Sitter will go on sale this October 25 and will be priced at 8,250 yen (P 3,242). It will be available through the Takara Tomy online store. No word if it’ll be made available for purchase outside of Japan.