Google launched the Pixel Buds 2 in April, six months after announcing the pair of wireless earbuds alongside the Pixel 4 series in October 2019. Priced at US$179, Google claims that the Pixel Buds offer high-quality audio from their 12 mm dynamic speaker drivers. The earbuds do not support active noise cancellation like the AirPods Pro or Sony WF-1000XM3 do, but Google claims that its Adaptive Sound technology allows the earbuds to minimise background noise.
The Pixel Buds have generally been well received too, with many reviewers concluding that the earbuds are worth the US$179 that Google is charging for them. However, as the earbuds started getting into the hands of consumers, complaints about audio issues started racking up on Google's support pages.
One of the most frequent issues that people encountered was a faint hissing or static sound. It is unclear whether all devices are affected by the issue, but only some people can hear it. Google then announced that it had fixed the issue and rolled out a firmware update in June. The company did not state that it had eliminated the issue, but it did report that firmware 296 "decreases the audio hissing/static noise that some of you may have experienced".
Google then released the Pixel Buds in the UK, complete with the hissing issue that should have been addressed in June. According to Chris Fox of the BBC, the sound is noticeable when listening to audio at low volume levels, but not exclusively so. Ultimately, it would seem that firmware 296 did not address the hissing issue for all of those who can hear it, despite Google's claims to the contrary.
Source(s)
BBC via r/GooglePixel, Google Support & 9to5Google