What the study did: The authors, mostly pediatricians and ear/nose/throat doctors, studied 14 different sound machines such as the Conair Sound Therapy device. They put the device on maximum volume and measured noise levels (in decibels) from 30, 100, and 200 centimeters (about 1 foot, 3 feet, and 6 feet) away. Distances were modified to correct for estimates of decibel levels in a 6-month old baby's ear canals. Distances were designed to represent "on crib rail," versus "beside crib," versus "across room" placements.
What the study found: All 14 devices showed volume levels greater than 50 decibels, which is the maximum volume threshold for hospital nurseries. Three devices, however, showed volume levels greater than 85 decibles, and one showed volume levels greater than 90 decibels! A decibel level of 85-90 is VERY loud, about the volume of a bus driving by you while you stand on the sidewalk. These levels exceeds current occupational health standards for adults. In other words, prolonged exposure to these loud devices is very likely to damage your baby's hearing.
Which sound machines damage hearing? Well, the authors do not reveal which of the 14 sound machines tested were the ones that made it over 85 decibels. An email and phone call to the lead author proved fruitless: they replied, but weren't willing to share any details regarding their methodology. This undermines the quality of their research and suggests they have a financial conflict of interest with the sound machine manufacturers, but we'll leave that up to the ethics committees at the Pediatrics journal.
So which sound machine should I buy? The take home message is to keep the volume at a reasonable level, and buy a sound machine with an auto-off timer. Babies' hearing is quite sensitive, so even at a low volume level (perhaps between a 2-4 on a 10-point volume scale) the sound machine should provide adequate background noise to soothe your baby. Be sure to check out our full list of the best baby sound machines.
Best sound machines of 2017?
Our recommended sound machines are:
1. Cloud b Sound Machine Sleep Soothers (with 5 cute options!). About $30, this is one the cutest, most reliable, and best reviewed sound machines on the market. Why do we think this is a good option for protecting your baby's hearing? Two things. First, it allows for full volume control, so you can set it on a nice low setting. Second, it has a built in shut-off timer that can be set for either 23 or 45 minutes. You can set it on a nearby surface, or use the velcro strap to attach it to the crib rail. It is not a basic utilitarian unit with a million different noises and features. It's a cute and simple alternative. Uses two AA batteries (included with purchase); with nightly use, expect them to last about 6 months. Here's a picture of the different varieties (click image for more information).
2. Cloud b Tranquil Turtle or Twilight Constellation Sound Machine and Night Light. About $45, this combines a cute and simple sound machine (2 sound options) with a night light. The blue "tranquil turtle" version (see picture below) projects a subtle ocean wave light, and the Twilight Constellation version projects a subtle starry night.Why do we think these are good options for protecting your baby's hearing? Same two reasons as with #1 above: you can personalize the volume, and it has a 23-minute shut-off timer. It also has adjustable night light brightness so you can customize that aspect as well. This only really works on a nearby surface, like on the top of a dresser, bookshelf, or changing table. Uses three AAA batteries (included with purchase); with nightly use, expect them to last about 4 months. Here's a picture of the Tranquil Turtle and some of the cute color options available with the Twilight Constellation version (click image for more information):