HomePod mini has hidden, unused temperature sensor

There is a temperature and humidity sensor that has been present in the HomePod mini since launch, but not used nor announced.

Missed by all teardowns at the time of launch, the HomePod mini is now revealed to have a sensor that is presumably planned for future use. There are still no specific details of its function or limits, but it is reportedly a sensor that measures temperature and humidity.

According to Bloomberg with assistance from iFixit, Apple has internally discussed deploying the sensor to relay that data to other devices. Unspecified sources say that it could be used to assist internet-connected thermostats.

Similarly, readings from the sensor that isn't in a good location to determine component temperatures could be used to trigger HomeKit actions. Potentially, a user could set a HomeKit-enabled fan to turn on when the HomePod mini reports the room reaching a certain temperature.

The sensor is in the base of the HomePod mini, next to where the power supply cable enters the unit, and is about the size of a grain of rice. Apple has not commented on its existence, and its HomePod mini technical specs do not list its presence.

However, as with all Apple devices, those specifications do list environmental operating parameters. HomePod mini is intended to be used only between 0 degrees Celsius (32 degrees Fahrenheit) and 35 degrees Celsius (95 degrees Fahrenheit).

Similarly, it's intended only for use when the relative humidity is what Apple describes as "5% to 90% non-condensing."

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26 Comments

ihatescreennames 1977 comments · 19 Years

About 3 years ago

AppleInsider said:

The sensor is in the base of the HomePod mini, next to where the power supply cable enters the unit, and is about the size of a grain of rice. Apple has not commented on its existence, and its HomePod mini technical specs do not list its presence.

This must be the spy chip that Bloomberg has been reporting on for so long!

afterfxguru 3 comments · 22 Years

The most likely answer is that it is to correct for how the audio is heard. Since temperature and humidity affect how sound is heard it makes great sense to put something like this in.

CloudTalkin 916 comments · 5 Years

afterfxguru said:

The most likely answer is that it is to correct for how the audio is heard. Since temperature and humidity affect how sound is heard it makes great sense to put something like this in.

That doesn't really make sense. People have been making sound reproduction devices for more than a century and none (that I know of) employ temp and humidity sensors to affect the sound. Your claim sounds a bit dubious, if I'm honest. Perhaps you have more info to support it. The most obvious reason it doesn't make sense? The sensor is inactive so it couldn't be contributing to how sound is heard.

This is most likely for a future Homekit elements like smart thermostat, humidifier, space heater, air conditioner, etc.

Mike Wuerthele 6906 comments · 8 Years

afterfxguru said:

The most likely answer is that it is to correct for how the audio is heard. Since temperature and humidity affect how sound is heard it makes great sense to put something like this in.

There is almost no computational audio in the HomePod mini.

dewme 5775 comments · 10 Years

CloudTalkin said:

afterfxguru said:

The most likely answer is that it is to correct for how the audio is heard. Since temperature and humidity affect how sound is heard it makes great sense to put something like this in.

That doesn't really make sense. People have been making sound reproduction devices for more than a century and none (that I know of) employ temp and humidity sensors to affect the sound. Your claim sounds a bit dubious, if I'm honest. Perhaps you have more info to support it. The most obvious reason it doesn't make sense? The sensor is inactive so it couldn't be contributing to how sound is heard.

This is most likely for a future Homekit elements like smart thermostat, humidifier, space heater, air conditioner, etc.

I agree with the latter post and speculation that this sensor pair is most likely targeting a smart home related function, like feedback for a smart thermostat and HVAC. The first post is entirely correct that sound propagation is absolutely affected by temperature, humidity, and also atmospheric pressure. If you live fairly close to a highway or railroad tracks that you only notice at night when the temperature drops you know all about temperature related sound diffraction. However, I would not expect that temperature or humidity related diffraction would be significant enough to notice within the small listening area and volume that a HomePod Mini is designed to support. But who knows, without doing the math.

It's also possible that these sensors are used to prevent the device from being operated outside of the temperature and humidity specifications. But since it's not hooked up, whatever it may be used for is a mystery.