The recording is noisy and low quality, which means that your brain has to do a bit of extra interpretation. This can be further complicated by how your device filters audio files and by whether your hearing is impaired at all (both of which reduce the amount of information making it to your auditory cortex).
If your device uses a high-pass filter and/or if you have mid-range hearing loss, you will only be able to hear “Laurel.” If your device uses a low-pass filter and/or if you have high-range hearing loss, you will only be able to hear “Yammy.” But if all of your devices have high fidelity speakers and you do not suffer from any significant hearing loss, then you will probably be able to hear both “Laurel” and “Yammy” (either simultaneously, or with minor changes in your listening condition).
That said, not everyone is going to process the audio file in the same way even if they don’t have any sort of hearing loss. So even though there is a plethora of tweets and videos that manipulate the clip in various ways (most often by changing the pitch), how much manipulation it takes for someone to hear it differently will vary (and some might never experience a change in how it sounds to them).