Sound measurement

Yes, it's a screen shot. I use it regularly to monitor input levels: I use Amadeus Pro. The version of Amadeus Pro on my older G4 Mac, which I use for a lot of transfers, doesn't have calibrations on its input meter, so ProLevel is very useful there. The later version of A Pro on my iMac does, but ProLevel is still worth using as it's a nice clear display, which also has a peak hold facility (so that above a certain level the highest bar on a peak remains lit for a second or so after the peak has passed, making it easier to read levels).

It does provide RMS (VU) levels as well but I ignore these: frankly VU meters are completely useless as you can easily overpeak on certain types of program without the meter showing it. I spent many years staring at BBC PPMs:

but I'm quite happy with ProLevel. One disadvantage is that it can't be made to read output levels if you want to check things after the event.

(Just for info: 6 on a PPM is equivalent to full modulation at the transmitter and maximum permitted level in a landline. 4 is the line-up tone level, which is 8dB below 6 and equivalent to 1 milliwatt - 0.775v - into the 600 ohms which was standard for a landline. Each gap between the numbered levels is 4 dB except for 6dB between 1 and 2: 1 is -25dB on peak and is the lowest permitted normal level for broadcasting - lower levels permitted for only 30 seconds. Present day digital recording set-ups are with 6 = -10dB on full modulation, above which serious clipping takes place. The meter rises fast but falls back slowly, over a second or so, to make it possible to read peaks.

The stereo version shows left and right on the left-hand meter and sum and difference on the right hand one. Maximum level on each of left and right is 1dB over 5 - 3dB below peak - to allow for the fact that when both are at this level the sum reads 6. If the difference is greater than the sum you've got a problem somewhere.

It all sounds a bit complicated but it's very easy to work with for long periods.)

DaveSL wrote:

All I want is a simple measuring device to sit on the sound output so that I can see the relative levels of my output, mostly sound effects for amateur shows.

I'm having a little trouble understanding your workflow. If these are prerecorded digitized sounds then I assume you are planning on resampling them at whatever level you want for the performance, & almost any app that does that has some kind of built-in metering at least adequate for judging relative levels. Most have waveform displays that let you judge the sound level of the entire sample at a glance without having to play it through from beginning to end while keeping your eyes on the meters. Even the free, open source app Audacity has that plus a spectrogram display option that shows level vs.frequency, which is often a much better indicator of relative (perceived) sound level.

They will also give you a good idea of how many bits of full scale resolution the sample uses to begin with, which indirectly tells you how much of that you can throw away when reducing the level of the resampled file before it starts to sound too artificial or pushes the noise floor too far up to be usable.

If you could explain a bit more about how you want to prepare the files for the performance it might help us suggest something more to your liking.

The software suggested is capable of far more than I require plus I have so far failed to get any to work as I want if at all.

If you mean QLab, I can't suggest anything to make it work as you want without understanding more about your workflow, but for the "at all" part, make sure you have a valid audio device assignment in QLab Preferences > Audio, something like this:

If you don't see any yellow "patch cords" QLab's output is not assigned to any output device. As for adding files to the cue list, you can just drag them into the large cue list area & drop them there. They will automatically be entered as audio cues. Make sure the Inspector is showing at the bottom of the window & select (highlight) one from the list. The "Level" tab in the Inspector allows you to set relative levels (& reads out in dB). If you click the big "Go" button to play a cue, you even get a peak-over-average level display in the onscreen channel faders.

ProLevel appears to only monitor the input mic and any possibility of seeing the sound output mutes the speakers. I have tried it with SoundFlower as well without success.

It sounds like you may not have not set the "Soundflowerbed" companion app to assign the 2 ch Soundflower output to "Built in audio" as explained in the second post of the forum link I mentioned earlier. Like with QLab, you have to route the output to something before you can hear it.

Are there any other options available?

There is always the "old school" approach of using a pair of real, external meters bridged across the Mac's output, which has some advantages (like not requiring any software at all). Aside from that, I can't think of anything useful, at least without knowing more about your planned workflow & what app(s) you intend to use for level shifting or playback.

Message was edited by: R C-R

I'm curious about what you mean about displaying the output as ppm. There is no measure of sound level I'm aware of that fits that description except maybe parts per million. For theatrical use, dB is usually the most useful measure of sound level because it matches fairly closely the sound level perceived by people. The ear can't detect small changes in level.

I'm also not sure what you are trying to accomplish. If you are trying to match the output level of your Mac to the input of the PA, as a general rule you should set the Mac system volume to at least 3/4 of maximum. Otherwise, the output will have more noise in it than is desirable & it will likely be audible through the PA even if you don't hear it through the Mac's speakers. It is best to set this volume control once & not vary it throughout a performance. The exact setting isn't critical, as long as it is relatively consistant throughout the rehearsals, sound checks, & performances.

I don't have any experience with it, but a quick search of the web turned up ProLevel, which seems to be the kind of thing you are looking for. It is free to try shareware, so you might want to check it out & see if it fits your needs.

Thanks for explaining the ppm reference. As you probably know, that BBC standard never caught on in the U.S. & most analog meters here are based on VU meter characteristics. In general, VU meters are probably better suited to theatrical work (because they indicate something much closer to perceived loudness) but I understand the desire to go with what you are most familiar with. I would have no idea what to do with a BBC meter calibrated with just a series of numbers going up to 7! 😉

I don't know what apps you have considered for your theater work but if you haven't tried it, I strongly suggest you check out QLab. It is purpose designed for live work, used in many professional theater productions, & best of all, the basic version is free (& quite capable).

Among its advantages are that you can record your effects, background music, etc. cues at maximum digital levels, taking advantage of all the bits of resolution your recording format allows, & set show levels within QLab. You can even set up fades, pans, & so on, & trigger them as separate cues or by running time of the track. It's all non-destructive, leaving the source files unaltered, & you can save different versions of the same cue set (a life saver when the show changes venue or the director can't make up his mind about levels for different cues).

You can also run additional cues while one is still running, either manually or by running time, which is great when say you want an environmental background sound effect running throughout a scene & also need to trigger other effects in sync with some action on stage.

I suspect you will find that this is a much better solution than trying to preset all your levels. In theatrical work, things rarely always go exactly as planned, & QLab is designed with that in mind. There is also a thriving support community of professional & amateur users willing to help out each other, a newsletter, & extensive documentation & tutorials available from the support page.

ProLevel is an input meter that runs independently of other software, displays RMS(VU) and peak levels, and runs on Tiger upwards. It's $20.

http://www.katsurashareware.com/pgs/prolevel.html

I mentioned & provided a link to ProLevel in my first reply. To monitor output levels, refer to the FAQ link on the web page, which leads to this.

Note: I am not a big fan of Soundflower because it seems to be implicated in causing some issues with normal system operation. At the least, I would not want it present on my Mac during a performance.

It does provide RMS (VU) levels as well but I ignore these: frankly VU meters are completely useless as you can easily overpeak on certain types of program without the meter showing it.

Keep in mind that when working with reasonably good quality PA systems, it is usually much more important to monitor average levels than peak ones. This isn't just because it is a better indicator of perceived loudness.

PA amps can deliver brief, undistorted peak power levels considerably higher than their RMS ratings indicate. Likewise, PA speakers are generally able to handle peak power levels considerably higher than average ones. Part of the reason for this is as the voice coil reaches the limits of its excursion, it begins to move out of the magnetic field gap, decreasing the force pushing it toward self destruction. This acts somewhat like built-in mechanical limiter. This does result in distortion but it doesn't rise to audible levels unless you overdrive the speaker excessively.

By far the most common cause of speaker failure is voice coil overheating. As it heats up, materials begin to soften & bubble, the coil binds in the gap, & it abrades itself to death or literally burns up. Because heating is proportional to RMS power level, peak readings don't tell you much about how (literally) hot you are running the PA.

And from a more practical standpoint, if you limit the PA to some arbitrary peak power level you aren't taking full advantage of its dynamic output capabilities. This means you will need a much larger & more expensive system than is actually necessary to produce the desired sound levels. In fact, if you use a peak limiter or compressor to do this, you can easily raise the average power level to the point that you are overheating the PA excessively, as well as compromising the dynamics of impulsive sounds that add realism & dramatic impact to theatrical performances.

PA of course is a different discipline. When I started in broadcast engineering (50 years ago!) there was no protection on transmitters, and an overpeak could take one off the air. (There must have been a slight overhead beyond 6 on the PPM, but it wasn't much.) Later on limiters were introduced to stop that.

Now of course with digital systems it's absolutely vital not to peak beyond maximum as it squares off and the distortion is horrendous. That's partly why the BBC allows a 10 dB overhead - personally I work to 4-6dB below peak, but mostly I'm transferring pre-existing archive material which has already been controlled.

R C-R wrote:

I mentioned & provided a link to ProLevel in my first reply.

So you did - didn't see it.

Roger,

The image you provided looks like a screen shot. Does that mean you use ProLevel? If so, DaveSl might be interested in your opinion of it, especially since you both are BBC guys.