
The proper question to get at this problem is: How do sound waves travel over the wires that connect the audio device and the headphones? This article will briefly describe the physics behind sound waves and then discuss the use of other devices along the headphone cord.

The effects of the alteration of cords on the sounds have more to do with the sound impedance of different types of end uses and the quality of the audio splitter material. No listener would be able to tell a difference in the quality of the sound. No, generally, 3.5mm audio splitters do not reduce the sound quality heard on multiple headphones to a perceptible degree. Do 3.5mm audio splitters reduce sound quality? It is valid to wonder if a splitter reduces the sound quality heard through the headphones. However, there is a constant concern about the degradation of the sound quality due to the inclusion of another piece of hardware into the listening experience. Enjoyment of a movie, clip, video, or song between more than one person is highly limited when you are in a crowded environment or workspace. The main benefit of using a splitter is the flexibility to operate multiple speaker devices at a time. This one splits a line into headphones and microphones to allow separate upgraded equipment to work in unison.

There are some that are specifically designed to combine audio or have separate audio inputs and outputs. Splitters one male end and two female ends ( example).

The audio is most commonly directed to two separate headphones. The main use of a 3.5mm audio splitter is to split the sound coming from a device like a mixer, smartphone, tablet, computer, or Sony Walkman.

If you have ever had an SO (significant other) that wants to mooch off your prior planning and listen to your movie on the plane as well, then you absolutely know why you need an audio splitter.
