When you are in a party with friends, a small amount of delay between you talking and the other player receiving it can be massively frustrating. Unfortunately, it is a common problem and it is still a problem with the PS5. The good news is that it is relatively easy to fix voice chat lag on the PS5.
Obtain an Open NAT Type
NAT type is a measurement of how restrictive your network firewall is. The scale on the PS5 goes from 1-3. If it is 3 you are most definitely going to have issues. If it is 2, you should be ok but it can sometimes cause issues. The aim here is to get an open NAT type of 1. This should allow your PS5 to communicate with the internet much better.
I had this exact issue with voice chat and it was no longer an issue once I had opened the ports on my router for the PS5 to communicate with the internet. This process can be quite detailed, so I would suggest you check out this NAT guide for the PS5 to open up your connection to improve voice chat.
Switch To a Wired Connection
Wired connections are far more stable than wireless since there is a lot less in the average home that can interfere with it. Some people often find their NAT type improves when they change to a wired connection. I understand this is not going to be possible for everyone, nobody wants a 30-meter cable running through the house but if it is easy to do so, definitely do it. This alone could be what fixes the voice chat lag. It is relatively effortless for those who have a console close to the router.
Check Your Network Connection
Voice chat lag could simply be caused by a lot of activity on your home network or some other interference in your home. Wifi signals are subject to interference with other wireless signals. Check the signal strength from the network settings on the PS5. Try running a speed test to see what your network is capable of. If numbers are looking bad, see if there are some devices in the house you can disconnect.
Check Your Headset
If your headset plugs directly into the Dualsense controller, you should be fine. The voice chat will be using the wireless connection that the controller is using. If the controller is working fine, the voice chat should be ok too. If you have a standalone Bluetooth headset that has its own battery and connects to the PS5 independently, check the headset to make sure it isn’t having some issues of its own that could be causing it to lag.
You can check the voice chat in the Ps5 system settings. You can speak and you will see the volume level increase and decrease. Use this as a measurement to see if there is a delay. If you speak and the PS5 does not receive it right away, you have found the source of your problem.