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Joined: 03 Apr 2006
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 Posted: Tue Apr 04 2006 13:09
Spectrum Analyzer question |
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Afternoon all,
No-one has ever been able to adequately explain the use of a Spectrum Analyzer to me before - can anyone shed any light?
I've had them recommended to me, I've even found a couple of good examples to download for free...
In theory, it sounds like a useful tool to help understand the dynamics and 'graphic signature' for a piece of music, however, it seimple (plain English) terms: what do you do with it? How does it help?
Or is it just me...
Thanks!! |
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Martin
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Joined: 05 May 2003
Location: Norway
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Posted: Tue Apr 04 2006 15:02
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I`m absolutely no expert on this - but if you look at the spectrum you can discover if some frequencies are too dominant.(like if there is to much bass).
This has to do with the dynamics of the song, because if the bass is to dominant the other sounds (mid and high frequencies) will be subdued (not stand out as much). What you want is a nice balanced soundimage and a spectrum analyser can help you with that.
EDIT: there is a really great article on how to understand this at dnbscene.com, but their website is down so I have enclosed the google cache link:
http://www.dnbscene.com/articles.php?mode=display&id=79
Google cache |
~ http://martin.madtracker.net ~ |
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Joined: 03 Apr 2006
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Posted: Wed Apr 05 2006 08:21
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Thanks, Martin - I'll go and have a look at your links.
I'd also wondered if the tool has any 'executable functions'.
i.e. can you press something that does something? Or does simply provide some kind of graphical report that enables the brainiacs amongst us to act accordingly.
(I know my avatar suggests I'm a brainiac but we all have to start somewhere - bwahey!) |
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Inge
Man-At-Arms
Joined: 04 May 2003
Location: Nieuw Lekkerland @ Holland
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Posted: Wed Apr 05 2006 08:40
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That depends on the exact analyzer you're using. Some are really only meant for analysis, others can also perform some mixing/mastering stuff like eq, compression and limiting. What is the name of the plugin? |
Care for a game of Monopoly? |
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Sunbuster
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Joined: 05 May 2003
Location: Finland
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Posted: Wed Apr 05 2006 19:10
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Basically, a spectrum analyzer gives a visualisation of sound (or any waveform signal for that matter) on three axes: Amplitude (volume if you like), Frequency and Time. This way you can see how a sound changes in both amplitude and frequency components over time. Often the 3rd dimension is represented by a color intensity instead of a 3rd axes. So if you have the frequency on the Y-axis and time on the X-axis of a graph, then the amplitude of the sound at a particular frequency and time can be represented by a color. A brighter color usually means a higher amplitude. Consider the following spectrums:
Figure 1: Orkidea - Unity
Figure 2: Orkidea - Unity (zoomed)
Figure 3: Rammstein - Mutter
Figure 1 shows a spectral view of Orkidea's track "Unity" as it's shown in Adobe Audition 1.5. Figure 2 shows the same thing, but zoomed in on the lower frequency ranges. What you can notice directly from fig. 1 is that the sound cuts almost completely above 16kHz (probably due to it being mastered for vinyl). Note the almost straight line around 1.5kHz (and at least one distinct line below that also) in the beginning of the track. That is produced by an organ playing a single note. So, by doing a spectrum analysis on an instrument you can see what frequencies are most important for that instrument. Thus you can use this to aid you in deciding what frequencies of an instrument to filter out in order to give some other instrument more space. Note that I said aid. The final decision of course has to be made using your ears.
What you also can see is that the spectrum is pretty bright yellow, almost white at the bottom of the graph (this is zoomed in in fig. 2). This indicates that the track is pretty heavy on the bass. This intensity ends almost completely before 500Hz. Most dance/trance/techno tracks will have something in this direction since bass is important for these genres, whereas rock/pop [See figure 3] will usually have a wider spread on the bright, meaning a more even balance in amplitude for different frequency components.
Figure 4: Dire Straits - Down to the waterline
Figure 5: Dire Straits - Down to the waterline (zoomed)
In figure 4 I have a graph of the Dire straits classic "Down to the waterline". In figure 5 I zoomed in on a couple of interesting features. It shows the quitar solo in the intro. Note how you can see the various harmonics of the guitar (the yellow dots/lines) and how they fade out. At the bottom you can see the bass coming in a couple of times. Again, this could be used by you to decide what areas of an instrument to filter out to give another instrument more space.
Figure 6: Dire straits - Sultans of swing
Figure 7: Dire straits - Sultans of swing (zoomed)
Figures 6 and 7 show the same procedure from "Sultans of swing". Compare figure 3 with figure 6 and you can see how the Dire Straits track looks more chopped up compared to Rammsteins track. Sultans of Swing is very clean in the sound. It doesn't have more than the bassline, kick, snare, hihats and the occasional ride and crash, the clean guitar and the vocals. All sounds have a fairly quick decay rate. Rammstein's Mutter on the other hand has a lot of distorted guitars that don't decay anything between notes, they create an even wall of sound. The drumming contains a lot of open hihats and crashes. Thus, based on spectrum analysis you could probably do a pretty educated guess on wether a track will sound clean or dirty.
Figure 7 shows the quitar solo in the end of Sultans of swing. Again you can see the harmonics and slides of the guitar.
Spectrum analysis thus can be used to figure out, like Martin said, what frequencies are dominating in a sound and how those frequencies decay or don't decay over time.
If you want to go completely overboard on the subject of spectrum analysis then here's a 120 page discussion on the matter:
http://cp.literature.agilent.com/litweb/pdf/5952-0292.pdf
Contains all the juicy technical and mathematical details I guess. I haven't read it yet, because, well, it's 120 pages 
hope this helped some and I didn't talk too much bullshit (please post corrections if I said something wrong). |
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QBical
Registered User
Joined: 04 May 2003
Location: Utrecht , The Netherlands
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Posted: Wed Apr 05 2006 21:36
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great post subuster!
But I tend to dissagree that a spectrum analyzer can help you out with your mix. Sure it gives an impression of the sound, but it won't tell you if it sounds good or bad, the only things that can do that are your ears in combination with your brains. So don't rely on Spectrum Analizers to much...
However, I use Spectrum Analizers quite often for re-synthesis, you take an instrument ( let's say a church bell ) and load the sample into a spectrum analyzer, then you can find out wich frequencies ( often called partials ) are playing in the churchbell and what there decay time is and so on...
Then you can reprogram this in an additive synth ( that's a synth with a lot of sine oscilators ) and you have a good recreation of a church bell...
neat tool :
Spear - A great way to see the partials of a certain sound, and you can get to shift them around, and extend them and stuff, REALY great on voice samples, try it! |
PC: P4 HT 3ghz, 1gb ram, 500GB+ Storage, plextor DVD-rw, M-audo Audiophile 2496
Laptop: Apple Powerbook G4 15inch
Other Stuff: Phonic MU802 mixer, Alesis M1 Active Mk2 Monitors, Ipod 2nd gen. 20GB, maxtor firewire HD 80GB |
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Joined: 03 Apr 2006
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Posted: Thu Apr 06 2006 13:39
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Well that's just the sort of answers I was looking for, guys!
Thanks, Sunbuster - I really appreciate the time you took to prepare your reply. What a great forum!
Now I just need to read it all again so I understand it... that's a lot of clever vyving...
Best,
CFG |
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Inge
Man-At-Arms
Joined: 04 May 2003
Location: Nieuw Lekkerland @ Holland
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Posted: Thu Apr 06 2006 13:45
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Serious: Sunbuster's reply must be one of the best I've read in ages. Can't we transform that in a nice tutorial for mt.org? |
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Sunbuster
Registered User
Joined: 05 May 2003
Location: Finland
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Posted: Thu Apr 06 2006 21:24
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| Inge wrote: |
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Serious: Sunbuster's reply must be one of the best I've read in ages. Can't we transform that in a nice tutorial for mt.org?
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Glad you liked it, feel free to do whatever with the post (or would you need me to do something about it?). I have it copied on my computer also, so if you in a blind rage suddenly decide to delete everything, the words will not be lost |
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Inge
Man-At-Arms
Joined: 04 May 2003
Location: Nieuw Lekkerland @ Holland
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Posted: Tue Apr 11 2006 21:53
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| Sunbuster wrote: |
| Inge wrote: |
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Serious: Sunbuster's reply must be one of the best I've read in ages. Can't we transform that in a nice tutorial for mt.org?
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Glad you liked it, feel free to do whatever with the post (or would you need me to do something about it?). I have it copied on my computer also, so if you in a blind rage suddenly decide to delete everything, the words will not be lost
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I would be very happy if you could chop it into pieces (three or four) and make distinct chapters of it. That way, it would be great for the tutorials section. The extra info by Qbical might be a nice extra chapter. Qbical: could you elaborate on what you exactly mean with re-synthesis? Or could you do that yourself, Sunbuster?
Thanks in advance! |
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Sunbuster
Registered User
Joined: 05 May 2003
Location: Finland
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Posted: Wed Apr 12 2006 09:07
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ok, I'll put it on my todo-list. Right now however I have a deadline with my thesis project coming up, so it might take a while for me to chop things up. |
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Inge
Man-At-Arms
Joined: 04 May 2003
Location: Nieuw Lekkerland @ Holland
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Atlantis
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Joined: 11 Feb 2005
Location: Hamilton, New Zealand
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Posted: Mon Apr 17 2006 09:23
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| Sunbuster wrote: |
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What you can notice directly from fig. 1 is that the sound cuts almost completely above 16kHz (probably due to it being mastered for vinyl).
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No, it's because it's an MP3.  |
Atlantis [Atlantean Records]
multiband professor/eq professor/Nur-Ab-Sal |
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Elijah
Registered User
Joined: 20 Jan 2004
Location: Calgary, Alberta, Canada Eh?
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Posted: Mon Apr 17 2006 16:01
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| Atlantis wrote: |
| Sunbuster wrote: |
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What you can notice directly from fig. 1 is that the sound cuts almost completely above 16kHz (probably due to it being mastered for vinyl).
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No, it's because it's an MP3.
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or some other form of compressed audio. however. the wee spikes coming out into the upper frequencies. make me say nay-nay
it kind of looks like a wav-pcm that was recorded directly from a record. |
- Elijah |
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Atlantis
User
Joined: 11 Feb 2005
Location: Hamilton, New Zealand
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Posted: Mon Apr 17 2006 18:48
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| Elijah wrote: |
| Atlantis wrote: |
| Sunbuster wrote: |
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What you can notice directly from fig. 1 is that the sound cuts almost completely above 16kHz (probably due to it being mastered for vinyl).
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No, it's because it's an MP3.
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or some other form of compressed audio. however. the wee spikes coming out into the upper frequencies. make me say nay-nay
it kind of looks like a wav-pcm that was recorded directly from a record.
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Interesting. If you observe an MP3 with a spectrum analyser though (the waveform type), there are still the occasional, low-level spikes above the cutoff, so based on this, and the sharp rolloff at around 16 kHz, I would think that it's a 128 kbps MP3. I never realised recording off vinyl produces such results, especially considering vinyl doesn't have a sampling rate, or at least I've read it's somewhat equivalent to 88.2 kHz, meaning frequencies right up to 44.1 kHz if properly stored - certainly not 16 kHz, or is it? |
Atlantis [Atlantean Records]
multiband professor/eq professor/Nur-Ab-Sal |
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