Ultrasonic noise is an inherent side‑effect of the DSD format — but it’s nothing to worry about!
I have recently started capturing my vinyl collection to DSD and hi‑res PCM, using the Korg DS‑DAC‑10R and Audiogate 4 software. The result sounds great but when I examine the audio file in iZotope RX 8 Elements I see a band of ultrasonic noise, which I’ve highlighted with a red box in the screenshot. Should I be worried about this noise? Will it do any harm to my equipment during playback? And if so, how do I go about removing it?
SOS Forum post
Technical Editor Hugh Robjohns replies: Ultrasonic noise is an inherent side‑effect of the single‑bit PCM format, which is what ‘DSD’ is. The format needs a heck of a lot of (ultrasonic) dithering, and that’s what you’re seeing in the spectrogram. It’s not really something to worry about — unless your pet bat starts complaining about headaches! It won’t harm your replay equipment, as it appears to be around ‑60dBFS. Your speakers/headphones/earbuds will be well into their natural roll‑off well before then too, and there won’t be enough energy to cause any problems to the drivers.
It’s not really something to worry about — unless your pet bat starts complaining about headaches!
Ultrasonic noise can potentially cause issues with intermodulation distortion in inferior electronics, but it’s very unlikely with anything modern and half‑decent.
If it worries you, a simple third‑order low‑pass filter set at 20‑25 kHz will do the trick, but this will also introduce HF phase shifts that the DSD format was intended to avoid, and you’ll need to save the processed file as ‘high‑res’ PCM (if you re‑encode it as DSD, all that ultrasonic noise will come right back).
So, I’d say if it sounds great, there’s really nothing to worry about, and you should stop looking for problems that don’t exist.