Where should I set the cutoff?

As high as the material allows. Music with cymbals and acoustic detail usually survives a corner in the 10 to 12 kHz region, while speech can go down to 6 or 8 kHz because very little consonant energy lives above that. Lower corners remove more hiss and more of the sound you wanted to keep.

Why does my recording sound dull afterwards?

Because a lowpass removes everything above the corner, including the air and sparkle in the original. The response is only 3 decibels down at the corner and rolls off at 12 decibels per octave, so the effect is gradual rather than abrupt but still real. Raise the cutoff or accept a little remaining hiss in exchange for the top end.

How is this different from the noise reduction tool?

This one applies a single filter and makes no attempt to model the noise, so it cannot introduce artifacts but also cannot separate noise from signal. The spectral approach estimates a noise profile and subtracts it, which removes more of the noise across the whole spectrum at the cost of a watery character when pushed.

Will it remove hiss from a recording where music is playing?

It will reduce it, with a catch: the filter takes the music's own high frequencies down alongside the hiss. If the hiss and the music overlap in the same range there is no filter that can tell them apart, so the result is a trade between brightness and noise rather than a free win.

What if the recording also has hum or clicks?

Deal with those first. A lowpass filter has no effect on a 50 or 60 Hz hum and none on impulsive clicks, so run the hum and click tools before this one, then finish with the hiss removal once the other problems are no longer masking the top end.

Hiss Remover

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Hiss Remover takes the steady high-frequency noise of tape, preamps and cheap converters down with a single gentle filter. It is the artifact-free kind of hiss removal: one lowpass with a corner you choose, rather than a spectral reconstruction.

What is Hiss Remover?

Load a file, drag the cutoff and the tool applies one lowpass filter across every channel. Tape hiss and preamp hiss both live above roughly ten kilohertz, while the musical energy of most material does not, and that gap is the whole basis of the approach. Everything well above the corner rolls off quickly and everything well below it passes through effectively untouched, which is why the honest guidance is to set the corner as high as the material will tolerate.

What the panel gives you:

A cutoff slider from 4000 to 16000 Hz in steps of 500, defaulting to 10000.
A second order lowpass, which is a 12 decibel per octave roll off rather than a brick wall.
A report line quoting the corner, the slope and the frequency below which content is effectively untouched.
A WAV download named after the source with a dehissed suffix.
Written guidance in the panel itself: 10 to 12 kHz for music, 6 to 8 kHz for speech.

The filter is a second order biquad lowpass designed with the standard RBJ coefficients and a Butterworth damping factor, which puts the response 3 decibels down at the corner and then falls away at 12 decibels per octave. That is a real filter rather than a noise model, and the distinction matters: it cannot tell hiss from cymbals, so it removes everything up top in equal measure. The payoff is that it introduces no artifacts of its own, which is more than can be said for aggressive spectral processing on quiet, wideband noise. Because the touch is so light, the whole file is processed in one pass with no tuning beyond the corner frequency.

When it is the wrong tool:

Hiss that overlaps the music's own high frequency content cannot be filtered away without dulling that content at the same time.
The roll off is shallow, so the noise is reduced rather than eliminated; near the corner you keep a good portion of it.
Setting the corner low to kill more noise costs you cymbals, consonants and air on voices.
Speech that has already been dulled by a lossy codec can sound noticeably muffled once more high end goes.
It removes treble from the entire file, including passages where no hiss is audible.
The processing is offline, so there is no way to audition corners inside the tool and no undo beyond reloading the original and running the pass again with a different corner.

Use it on transfers of tape, vinyl captures and any recording where the noise floor is bright and the useful content is not. Match the corner to the material: music with cymbals usually tolerates 10 to 12 kHz, while a spoken-word interview can go down to 6 or 8 kHz and sound better for it. If the hiss is not the only problem, deal with hum and clicks first, because a lowpass will not touch either of them, and a pass that dulls the top end is far easier to judge once the noise underneath has already gone.

How to use Hiss Remover

Choose the file that needs brightening down, such as a tape or vinyl transfer.
Set the cutoff: about 10 to 12 kHz for music, and 6 to 8 kHz for speech-heavy recordings.
Click Remove hiss to run the lowpass across every channel in one pass.
Download the dehissed WAV and check that cymbals or consonants still sound natural before accepting the setting.

When to use Hiss Remover vs related tools

Hiss Remover suits bright, steady noise sitting above the useful content, which is why it is the first thing to try on a tape or vinyl transfer. Noise Reducer is the spectral alternative for broadband noise that runs across the spectrum rather than above it, and Background Noise Remover handles tonal hum instead of a spread of high frequencies. When the excessive brightness is concentrated on sibilants rather than the whole top end, Sibilance Reducer ducks just the offending band instead of everything above a corner.

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