Notch is a very narrow and precise cut or attenuation of a specific frequency or frequency range, typically used in audio engineering and music production.
What is Notch in Audio Production: Table of Contents
If you’ve ever twiddled the knobs on an audio equalizer, you’ve likely seen parametric EQs with a control called “Q” or “Quality Factor”. This allows you to make precise, narrow cuts or boosts at specific frequencies. When used to make narrow cuts, this technique is called a “notch filter”.
In simple terms, a notch filter precisely targets and removes a very narrow band of frequencies from a signal. It’s like surgically slicing out a sliver of audio spectrum. This differs from broader EQ cuts that attenuate wider swaths of frequencies. The key is the narrowness and precision of the notch.
The Curious Case of the Notch Filter: What’s In Store?
Notch filters may seem like obscure audio sorcery, but they’re invaluable tools for taming problematic frequencies. We’ll unravel the mystery of these precise frequency scalpels and explore:
- How notch filters work technically
- Classic notch filter use cases like feedback and noise reduction
- Creative notch filter techniques for sound design
- Best practices for surgically notching your audio
- Notch filters vs. other EQ methods like hi/lo-passing
- Pro tips and common questions about notching frequencies
By the end, the unique powers and pitfalls of notch filters will be clear. You’ll level up your EQ skills and be notch-ing like a pro in no time!
What is a Notch Filter?
In technical terms, a notch filter sharply attenuates or cuts a very narrow band of frequencies from a signal. We’re talking surgical-precision narrow.
Visualize an EQ graph with frequency on the X-axis and amplitude on the Y-axis. Now imagine a single, narrow, deep cut penetrating into this graph. Congrats – you’re visualizing a notch filter!
It’s essentially creating a notch or slice at one specific frequency. This differs from wide-band EQ cuts that attenuate a whole range of frequencies.
The Skinny on Q: Controlling Notch Width
The “Q” or “Quality Factor” determines the width of the EQ cut or boost. A higher Q value makes an extremely narrow notch. Lower Q creates wider EQ bands.
For notch filters, we want high Q values to slice out only the smallest sliver of bothersome frequencies. Low Q would make the cut too wide and impact more of the audio spectrum.
Why Such Narrow Notches?
You’re probably wondering why we bother with these narrow notches instead of just doing a standard EQ cut.
It’s all about surgical precision. Broad cuts make blunt changes to the overall tone. But a notch can pinpoint and remove just one problematic frequency without damaging the rest of the sound.
It’s like using a scalpel versus an axe – notching allows refined, frequency-specific sculpting. This surgical analogy will make even more sense when we explore notch filter use cases!
Why Use Notch Filters in Audio Production?
Notch filters may seem obscure, but they’re invaluable problem-solvers and creative tools. Let’s explore the core benefits and use cases.
Notch Filter Superpowers: Precision, Control and Surgical EQ
Notch filters enable precise removal of problematic frequencies without damaging the surrounding audio. This surgical approach simply isn’t possible with standard EQ cuts.
You can notch out unpleasant tones, noises and rumbles – improving the sound without bluntly hacking away at the EQ spectrum. Notching gives refined, frequency-specific control.
Feedback Buster: Notch Filters Zap Pesky Feedback
We’ve all heard the shrill squeal of audio feedback. It happens when mics pick up sound from nearby speakers, creating a loop. Certain frequencies get amplified intensely, causing painful feedback.
Notch filters can pinpoint and cut those exact feedback frequencies for a quick fix. No more ringing ears or interrupted performances!
Hushing Hum and Noise: Notch Out Offending Frequencies
Unwanted hum or noise can sneak into recordings and live performances in many ways. Notch filters can isolate and cut specific frequencies causing hum or noise, cleaning up the audio.
Whether it’s 60Hz electrical hum, amp buzz or a talkative fan, notches can target the frequency and slice it out. No more distracting noises!
Sculpting Sound: Getting Creative With Notch Filters
Beyond problem-solving, notch filters also enable creative sound design. Surgically cutting certain frequencies can dramatically alter the texture and tone of sounds.
For example, you could notch out some midrange frequencies from a synthesizer to create a hollow, ghostly quality. Or notch the highs for a muffled effect. The possibilities are endless!
Best Practices for Notch Filter Use
Like any powerful tool, notch filters can be misused. Let’s review some best practices.
Steady Hand Required: Don’t Over-Notch!
Used sparingly, notch filters are great. But it’s easy to get notch-happy and overdo it. Too many narrow notches can make things sound odd and hollow.
Always listen critically when notching frequencies. Less is often more – only notch the bare minimum to achieve your goal. And use your ears, not just your eyes – don’t obsess over the EQ graph.
Consider The Source Sound and Desired Effect
Not all sounds should be aggressively notched. As you notch frequencies, consider the core qualities of the original sound. Is notching removing something essential?
Also consider the desired effect. Do you want a subtle change or total transformation? Your goals should guide how drastically you notch the sound.
Phase Cancellation: Avoid Notch Filter Pitfalls
One risk with notch filters is accidentally creating phase cancellation issues. This can happen if you notch the same frequency on multiple tracks.
The notched frequencies can cancel each other out, creating an even bigger dip in the full mix. Always check solo’d tracks and full mixes to catch any phasing issues before they become a problem.
In general, use notch filters surgically and transparently. Let the fundamentals of the sound shine through while precisely targeting only the unwanted frequencies.
Notch Filters vs. Other EQs: Know Your Options
Notch filters aren’t the only EQ option. Let’s compare notching to high/low passing and wide boosts/cuts.
Notching vs. Hi/Lo Pass Filters
High and low pass filters attenuate all frequencies above or below a set point. This is broadband filtering.
Notch filters target specific frequencies between the highs and lows. This surgical approach spares more of the EQ spectrum.
For example, a high pass filter starting at 500Hz would cut bass below 500Hz. A notch at 300Hz only cuts that narrow band, preserving more low end.
Notching vs. Wide EQ Boosts/Cuts
Wide EQ boosts and cuts alter a broad range of frequencies. Notching has a much more focused effect.
A 6dB cut from 500-1000Hz makes a broad change to the midrange tone. A 6dB notch at 700Hz only cuts that small slice.
Choosing Your EQ Weapon Wisely
Reach for notch filters when you need to precisely target narrow problem frequencies without altering the overall sound.
For quick, broadband tonal shifts like brightening or bass boosting, broader EQ changes often work better.
Combine both techniques – notch to address specific problems, then use wider EQ moves to refine the overall tone.
The key is understanding when narrow surgical notching is needed vs. when broader strokes are appropriate. Master both techniques to unlock pro-level EQ skills!
Pro Notch Filter Secrets Revealed
Let’s dig into some savvy techniques to truly master notch filters.
Final Polish: Careful Notching During Mastering
Notch filters work magic when mastering and putting the final polish on a mix. You can notch out any last hints of harshness, mud or odd resonances.
Just be cautious – only make subtle notches at this stage to refine things, not dramatic changes.
Stacking Notches: Combine Multiple For Complex Solutions
Having trouble taming a wild frequency? Use multiple notch filters together. This enables more complex precision targeting.
Maybe 160Hz is booming and 170Hz is honky. Stacking two narrow notches right next to each other could solve that.
Automation: Notch On The Move For Dynamic Mixes
Notch filters don’t have to be static. Through automation, the notched frequency can move around over time for dynamic mixes.
As one frequency becomes problematic, just notch it out. When it’s no longer an issue, automate the notch to fade away.
Track vs. Bus Notching: Choose Wisely
Should you notch on individual tracks or full mix buses? The answer depends on your goal.
For per-track issues like problem resonances, notch those tracks. For issues only audible in the full mix, notch the master bus.
Let your ears be the guide – notch where it best solves the problem with the least collateral damage.
Notch filters take finesse and nuance to master. Hopefully these pro techniques will notch your skills up to the next level!
Common Questions About Notch Filters
Let’s tackle some frequent questions about these precision tools.
Do I Need Fancy Plugins for Notch Filters?
Nope! Any parametric EQ plugin with adjustable Q/bandwidth will give you notch capability. Even free EQs like ReaEQ in Reaper or EQ Eight in Ableton can create razor-sharp notches.
The key is finding EQs that allow you to crank the Q factor up very high. But you don’t need expensive third-party plugins to start notching frequencies.
How Narrow Should My Notch Q Be?
There are no rules – let your ears guide you. Start with a very narrow Q and loosen as needed. Watch that excessive narrowing doesn’t audibly distort the sound.
For surgical fixes, aim for the narrowest notch that solves the problem. For creative effects, experiment with width to suit the desired tone.
Will Notching Cause Artifacts or Damaging Phase Issues?
It’s unlikely with sensibly used notches. The key is avoiding extremes like notching by 30dB or notching multiple tracks identically.
Do your notching in moderation and avoid notching the same frequencies on left/right channels. Always playback your notched audio critically to spot any artifacts.
Should I Use Notch or High-Pass Filter?
If you only want to attenuate everything below or above a certain frequency, use high or low-pass filtering.
Reach for notch filters when you need to surgically remove narrow slivers within the audible range. They complement hi/lo-pass filters nicely.
Is notching mainly used for problem-solving or can it be creative?
Notch filters are incredibly versatile tools that can be used both correctively to address issues like feedback and noise, and creatively to alter the texture of sounds during sound design. Precisely notching certain frequencies when mixing can solve problems without damaging the overall tone. Notching can also transform synth tones and SFX by surgically removing frequencies.
How do I know what frequencies to notch out?
It takes critical listening to identify problematic frequencies that are candidates for notching. Narrow down the bothersome frequency range, then sweep a narrow notch filter to pinpoint the precise frequency that needs attenuation. For creative notching, experiment with attenuating various frequencies to achieve your desired effect.
Should I notch frequencies on individual tracks or the full mix bus?
It depends on the context. Notching on individual tracks can tackle issues stemming from those tracks before the mix stage. But some problems like harshness may only reveal themselves in the full mix, in which case notching the master bus makes more sense. Trust your ears.
What’s the difference between notch and low/high pass filters?
Notch filters surgically attenuate very narrow frequency bands, leaving surrounding frequencies intact. Low and high-pass filters completely cut away all frequencies below or above a set point, performing broad strokes rather than targeted notching.
Can notch filters cause phase cancellation issues?
Yes, improper use of notch filters can potentially cause phase issues. Notching the same frequency on separate tracks can cancel out that frequency. Always solo tracks and check the full mix to catch any phase cancellation. Avoid notching the same frequency in both stereo channels.
What’s the difference between notch and shelf EQ filters?
A shelf EQ uniformly boosts or cuts above or below a set frequency. A notch filter makes a narrow, targeted cut at one frequency with minimal impact on surrounding frequencies. Shelves make broad tonal shifts; notches surgically slice specific frequencies.
Can notch filters produce harmonic distortion?
If taken to extremes, yes. Excessively narrow notching with an ultra-high Q or drastically cutting frequencies by 30dB or more can certainly introduce audible artifacts and harmonic distortion. Maintain a balanced approach and avoid over-notching to prevent this.
Are comb filters and notch filters the same thing?
No. A comb filter introduces regularly spaced spikes and dips in the frequency response. A notch filter makes one narrow, targeted attenuation of a specific frequency. However, a comb filter essentially contains multiple notches at various frequencies.
How do I check for audible artifacts from over-notching?
Carefully listen to your notched audio on multiple systems, checking for anything unnatural or abrasive. Bypass the notch filters to compare before and after. See if any frequencies become strangely exaggerated. Use reference tracks to help identify any artifacts.
What’s the origin and history of the notch filter?
Notch filters emerged in the 1960s from telephony systems engineering. They were used to combat signal interference by sharply attenuating specific “notch” frequencies. This surgical approach was revolutionary compared to previous filters. Notch filters later became indispensable studio tools.
What’s the difference between fixed and sweepable notch filters?
A fixed notch filter sits statically at one set frequency. A sweepable notch allows the attenuated frequency to be smoothly adjusted up or down. This allows you to zoom in on the optimal notch frequency based on what you’re hearing.
Can excessive notching cause listener fatigue?
Absolutely. Over-notching can make mixes sound unnaturally hollow and dull, especially with overlapping notches. This excessive EQ carving can fatigue the ears. Strive for tasteful, transparency notching that maintains the core tone.
Should I notch frequencies before or after compression?
As with any EQ moves, notch filters generally should happen pre-compression. Notching unwanted resonances early on will prevent them from triggering compression later. However, some subtle notch tweaks during mastering may occur after compression.