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Audio Responses


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Detecting started out as an audio-only hobby, and for us prospectors it mostly remains that way. Even if you are just swinging a VLF you can't trust the VDI numbers in hot ground. Beep, beep, dig. Now the more experienced detectorists know that there is a lot more to audio signals than just beeps. There is shape, tone, volume, sharpness, rhythm. It becomes a musical performance that we get to decode with our brains to decide whether a target is worth busting out the pick for.

Why have detector companies not put more emphasis on developing audio responses? We get screens, target ID's, GPS, wireless audio, but the same old sounds. But the most important user experience - the sound the detector makes - has not changed much. For all-metal VLF or PI detectors you get a VCO audio response that rises with signal strength. That's it.

Ok, so rant mode off, now my pitch.

A simple mapping of a normal VCO (voltage-controlled oscillator) audio signal is SIGNAL STRENGTH = PITCH and VOLUME change. This goes back to the time when a hardware oscillator was directly tied to the audio output and use the signal voltage to create an audio signal. You get a zip on all targets, and though the shape of the signal will vary based on what the target is, there is no indicator of target phase (or X/Y component). You want any audio info on that for a VLF, you have to switch to a tone mode.

Here is what a boot tack and and nugget sounds like on a VLF with a normal VCO audio (like a gold machine or all-metal mode):

1706240907_ScreenShot2020-08-06at12_23_53PM.thumb.png.6998c4e793c1992fb3d77596bf2d7a2b.png

Now if you were to instead tie the PITCH of the signal to the PHASE, and the VOLUME to the STRENGTH, you would get more information. It might look like this:

387075937_ScreenShot2020-08-06at12_21_37PM.thumb.png.0eb659ef5ef0509caaa5e7efcaa3d745.png

You can get a response similar to this by using 50 tones on the Equinox, but to my knowledge, no detector uses this kind of audio mapping in VCO mode. Do you see how much more information this would present to a seasoned detectorist? Especially with iron targets, which tend to have a very confused signal, the pitch would jump all over and should be easier to distinguish.

I believe this type of audio response might be able to be used with the GPZ (it's kind of there already with the hi/low tones) or any other detector that reads X and Y signal responses. Instead of having both PITCH and VOLUME tied to the composite signal like it's 1950, the responses would be independent and give the user more information - no screen required. For beginners this would not be good since it is hard enough for them.

Hope this makes sense, let me know what you think (especially CARL).

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Sounds great to me. Audio nuances are a very important part of evaluating a target. If a detector can carry out the nuances needed for proper id. My old GB2 had several nuances that really helped to id and evaluate digging or not.

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  The best audio processor ever made is still the one between your ears. But I concur with tboykin that with today's tecknawlogee you would think that there would be a great leap forward in the audio department of a detector.

  So how bout a trainable detector where each time you find a target it stores all the audio information for each target and  you push  button that that says "good target" (gold for nugget hunting / non ferrous for coins an relics) or" bad target" (hot rocks / trash) so that after a couple of hundred target digs the detector would be "trained".

  I think about these things because there is no depth to my laziness.

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20 hours ago, tboykin said:

I believe this type of audio response might be able to be used with the GPZ (it's kind of there already with the hi/low tones) or any other detector that reads X and Y signal responses. Instead of having both PITCH and VOLUME tied to the composite signal like it's 1950, the responses would be independent and give the user more information - no screen required.

I'm not sure I understand what your graph axis' represent entirely here, but if I understand what you are saying then I think the GPZ already does this. It's what people call the "warble". To me it sounds more like a tone curl than a warble as it "feels" like the audio is curling down or up and then back normal. It reminds me of those portamento things on 1980's synthesizers/organs that you could play by sliding a finger back and forth to bend the tone (or a bit like a whammy bar on a guitar). It's often encountered with tiny iron targets or bits of wire, especially curled or bent. But tiny nuggets, nuggets with odd geometries such as wire, prickly, or bent can also cause the response. And (so I hear) too can deep, very large nuggets, but I wouldn't know about such things. :biggrin:

I pretty much ignore "professional detecting style" advice. Along the way, I realized that this tone curl on the Zed can actually be induced on certain targets by not having a perfectly flat swing over the target, and angling your coil up or down on one side depending which way you swing, or by moving the coil up and down slightly as you push forwards and backwards over the target, sometimes angling side to side there too can induce the tone tone curl. Some targets you cannot do this on no matter what. When I can induce the tone curl by moving my coil like that, I can in some specific areas where I'm familiar with the native gold, discriminate targets with a fairly high level of accuracy if the iron junk is mostly wire bits or small tin bits. So, my swing is actually not flat at all most times in those areas, but intentionally skewing about to try to induce different effects on targets in the GPZ audio.

I'm not sure if that's what you mean though, as I'm not sure if that audio response is dependent on the signal phase or not, since I don't really understand ZVT all that deeply or how the GPZ processes audio.

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4 hours ago, klunker said:

So how bout a trainable detector where each time you find a target it stores all the audio information for each target and  you push  button that that says "good target" (gold for nugget hunting / non ferrous for coins an relics) or" bad target" (hot rocks / trash) so that after a couple of hundred target digs the detector would be "trained".

When processing audio the audio takes up so much memory that you would not have enough storage room to handle that much information. When you use a phone to video anything the thing that uses the most memory is the audio not the video. The ratio is close to 10 to 1 when talking audio versus video.

That is probably the main reason it is not done, there would not be enough room for the detector to store all the information.

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6 hours ago, tboykin said:

Detecting started out as an audio-only hobby, and for us prospectors it mostly remains that way. Even if you are just swinging a VLF you can't trust the VDI numbers in hot ground. Beep, beep, dig. Now the more experienced detectorists know that there is a lot more to audio signals than just beeps. There is shape, tone, volume, sharpness, rhythm. It becomes a musical performance that we get to decode with our brains to decide whether a target is worth busting out the pick for.

Why have detector companies not put more emphasis on developing audio responses? We get screens, target ID's, GPS, wireless audio, but the same old sounds. But the most important user experience - the sound the detector makes - has not changed much. For all-metal VLF or PI detectors you get a VCO audio response that rises with signal strength. That's it.

Ok, so rant mode off, now my pitch.

A simple mapping of a normal VCO (voltage-controlled oscillator) audio signal is SIGNAL STRENGTH = PITCH and VOLUME change. This goes back to the time when a hardware oscillator was directly tied to the audio output and use the signal voltage to create an audio signal. You get a zip on all targets, and though the shape of the signal will vary based on what the target is, there is no indicator of target phase (or X/Y component). You want any audio info on that for a VLF, you have to switch to a tone mode.

Here is what a boot tack and and nugget sounds like on a VLF with a normal VCO audio (like a gold machine or all-metal mode):

1706240907_ScreenShot2020-08-06at12_23_53PM.thumb.png.6998c4e793c1992fb3d77596bf2d7a2b.png

Now if you were to instead tie the PITCH of the signal to the PHASE, and the VOLUME to the STRENGTH, you would get more information. It might look like this:

387075937_ScreenShot2020-08-06at12_21_37PM.thumb.png.0eb659ef5ef0509caaa5e7efcaa3d745.png

You can get a response similar to this by using 50 tones on the Equinox, but to my knowledge, no detector uses this kind of audio mapping in VCO mode. Do you see how much more information this would present to a seasoned detectorist? Especially with iron targets, which tend to have a very confused signal, the pitch would jump all over and should be easier to distinguish.

I believe this type of audio response might be able to be used with the GPZ (it's kind of there already with the hi/low tones) or any other detector that reads X and Y signal responses. Instead of having both PITCH and VOLUME tied to the composite signal like it's 1950, the responses would be independent and give the user more information - no screen required. For beginners this would not be good since it is hard enough for them.

Hope this makes sense, let me know what you think (especially CARL).

I cannot verify it, but I am pretty sure the Deus also does this in Pitch tone mode and gold field mode as well.  There is a marked difference between the zip of different non-ferrous targets (and not just due to signal strength) so I do think that differences in phase shift response are baked into the Deus VCO emulating pitch tone mode.  It is not as pronounced as the way tone ID can differentiate targets in Deus "full tones" but pitch is not subject to some of the implementation issues associated with full tones on the Deus such as the fact that you have no iron volume capability when you apply disc unlike the multi tone and pitch modes where you can apply disc and still have the discriminated ferrous region provide an audible "iron volume" if desired.  This results in a very powerful and starkly contrasting audio attack when using pitch audio combined with iron volume for the discriminated ferrous region.  You get the low frequency iron grunts when passing over discriminated targets and then the distinctive pitch zips when you pass over a non-ferrous target.  It really makes those non-ferrous targets pop out of thick ferrous site situations.  Some may ask why bother to add discrimination if you are just going to listen for the ferrous tones anyway.  The reason is that you need to apply discrimination to set the tone break for iron volume (otherwise all targets ferrous and non-ferrous will simply pitch zip).  The other reason is because the addition of ferrous disc tends to keep iron from down-averaging the non-ferrous target IDs (yes in pitch mode you still have a fully functional target ID display).  Differentiating the phase shift aspect of the pitch audio is very nuanced.  It is more of a feel thing.  You do need to glance at your display to view target ID as an additional input to aid in a definitive "dig decision".  Gold Field mode (which is a pseudo "all metal" mode on Deus and Orx) does not use discrimination, so although Gold Field is similar to Pitch mode with the exception of the iron volume capability.  Orx does have a slight "iron volume" capability in Gold Field but it is not as pronounced as the iron volume on the Deus in discrimination mode.  Orx does not have a pitch tone mode option in discrimination mode - pity because if it did, I feel I could probably get rid of my Deus for the Orx and feel that I am not missing any capability.  Without pitch audio, I consider the Orx to be capable in a pinch but not equivalent or superior to Deus and I have found some great relics with the Orx.  Overall, I prefer the Deus implementation of pitch mode vs. full tones, and Gold Mode and also I prefer it over 50 tones and the Gold Mode VCO tone on the Equinox.  I can hear a lot of heads exploding after reading this, sorry about that.

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I agree the 7000 has a definite warble over certain nuggets. I also agree (I think), with the shorter duration of a bit of gold vs a boot tack although they can both be eerily (and disappointingly), similar. I also remember hearing a warble-sound that was just a bit different but just as tell-tale on the 5000 on certain gold bits. fwiw.

 

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The best processing happens between your ears. It's the difference from being able to drive formula one and an auto family sedan.

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2 hours ago, Reg Wilson said:

The best processing happens between your ears. It's the difference from being able to drive formula one and an auto family sedan.

I dig everything, also for my mental sanity. At night when I am home I wold think of all those undug targets

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