Moaning
This upgrade adds moaning sounds to your doll.
How it works
Sensors are fitted into the doll's main "erogenous zones". Mainly these are the breasts, thighs and crotch area. These sensors respond to touch and changes in position, and send a signal to a speaker. The speaker is most often located in the doll's neck, or near the underarm (depending on the brand).
When you squeeze or touch these areas, the doll starts making moaning sounds. The volume of the sounds doesn't depend on your actions. These are pre recorded sounds that are triggered when the sensors are activated.
The sound module runs on a battery located inside the doll. So you don't need to keep the doll plugged into the mains for the module to work. The charging port for the battery is located near the speaker.
Realistic expectations
It's important to understand this is simple mechanics: a sensor triggers, a sound plays. The doll doesn't "respond" to the intensity or nature of your actions, the sound library is limited, and the sounds start to repeat over time. For some users, the moaning noticeably enhances immersion, especially at first. Others switch the module off after a couple of months. Bear this in mind when making your decision.
Alternative to this option
Instead of Moaning specifically, any other moaning audio played from a phone can work just as well. Place it next to the doll, press play, and you'll get essentially the same effect.
Is it worth adding
This is a matter of taste, not a Must Have. If silence during use of the doll breaks the atmosphere for you, Moaning solves that problem inexpensively. If sound isn't critical for you, feel free to skip this upgrade: it has no effect on the doll's realism.
Like any other electrical upgrade in the doll, this option is sensitive to moisture. For a TPE doll this requirement is stricter than for a silicone one: a TPE model needs washing more often, so contact between the electronics and water is more likely. Before washing the doll, check the location of your model's sensors and speaker. The charging port can be covered up beforehand as an extra precaution.
There's no such thing as a perpetual motion machine. All electronics have a lifespan, and the sound module is no exception. The battery loses capacity over time, and the sensors lose sensitivity. That said, the doll herself isn't affected in any way if the module fails, she simply stops making sounds.