I can't specifically speak to the sound of any d5 or ddc pump but I have owned the h60 and I'm currently using the alphacool dc-lt ultra low noise (same as the lt240) and I have it set currently to a point where I can't hear it at idle. This is a cautionary tale because I don't have a lot of experience and I'm not yet sure what the longevity of any of it will be. So I have this pump currently running a 280mm rad with a full custom loop on a 2070 super and r5 3600 and the eisstation dc-lt 80 (the bigger brother to
@fabio dc-lt 40) which has a small res. I'm going to try to keep this info to purely the pump and preface with I'm ridiculously sensitive to noise.
So this pump can be ran at 12v (stock), 9v or 7v. So at stock voltage and the pump running 100% it sounds okay. It's more of a louder deep hum compared to the high pitch of the h60. Probably around the same sound level since they run 100%. I'm using the Strix x570i and it allows me, using DC mode, to drop the pump to 60% duty which I did. I set this for my idle temps and it's definitely quieter but it changes the frequency of the noise to be a higher pitch sound kinda like the h60 but quieter. I could hear it at idle if there weren't any other sounds. Which there tends to not be because the noctua 140mm fans are insanely quiet. It's not bad at all though. Most of the time you probably won't notice it.
Now, this is the part where I'm not sure if I should be doing it or not. So I got a 12v to 7v phoyba adapter to hard limit the voltage down. This is safe to do per alphacool's site. However, with the 7v adapter on you can still limit it on the motherboard. So at idle it is 100% quiet at 7v and 60% duty. Again not sure if I really should be doing this but temps are fine. GPU in the 30s and CPU bounces in the 30s-40s like it did before the 7v adapter. Now I have it set to run at 100% when it hits 49c because it was causing the GPU to get a litter warmer since I haven't figured out how to make the pump respond to the coolant instead of the CPU, which is fine because at idle it doesn't hit this and at load without it the GPU was getting warmer than I wanted. Overall temps are up 10c on the GPU and 5c on average with the 7v adapter under load.
So summary is for me idle noise with the 7v adapter is great. I honestly can't hear it. Even set to 100% it sounds better with it than 60% duty on 12v. However, there is a trade off of temps. I'm looking at low 70s on gpu under load and mid to low 60s on gpu during gaming and heavy CPU loads max out at 70c all on 7v. The 12v sees a max of mid 50s to low low 60s on both GPU and CPU while gaming and benchmarking, and during heavy CPU load max 66. Overall most people will have zero issue with the 12v set even at 100% but it is noticeable. Remember this isn't scientific stuff but I did do my best to monitor everything the same way. I don't have a accurate way to measure the decibels but I'm doing the perceived noise. I also don't recommend doing a double limit (I'm assuming the voltage is being limited twice) unless someone else can say it is 100% fine. I would recommend the 7v over stock if you are okay with the temps as my personal preference.
EDIT: Okay so the Strix mobo isn't monitoring or isn't reporting the same CPU temps that MSI Afterburner or HWInfo are. It must be looking at at different temp from the CPU. So my temps on the 7v were not with the pump actually running full 100%. Retesting I can't hear the pump at 7v 100% with any noise at all and my temps are much closer to the 12v temps. Maybe 3c higher on each during gaming loads. I will keep testing.