A career choice: fixing audio issues in CM!

[Rsachi]

Here is a fine article in the Hindu:
http://www.thehindu.com/education/caree ... 136663.ece

I liked this para:

A trained audio engineer will have a thorough knowledge of working with musicians, music directors, dubbing artists and filmmakers. The key is the amount of practical time they get to handle technology when they are getting trained for the business. Of late, an ideal mix— breed of audio engineers-cum-musicians are evolving, thanks to the perfect integration of aesthetic and technology while imparting formal education.

[harimau]

If you fix the ego issues, then the audio issues fix themselves by going away.

There was a time when there were no microphones.

Then there was a single microphone in front of the singer.

Then came multiple microphones.

Then came the demand for feedback monitor.

Now you have everyone on stage demanding his volume be increased.

Not content with that, we have singers saying, "Give me some sharp", or "Increase the bass", or "Add some reverb".

Did Semmangudi Srinivasa Iyer tell the audio technician to modify his nasal tone?

God gave you a specific voice; live with that. Don't try to fool the audience by adding bass or sharp or increasing mid-frequencies or whatever you want done.

Chenaging the tonality will not improve the quality of your music.

Or, we the rasikas are willing to put up with a less than perfect voice if the music is good.

Blaming the audio technician reminds me of the old saying: A bad craftsman blames his tools. |(

By the way, that article seems to be written by someone running a school for technicians and sounds like a recruitment advertisement.

[Rsachi]

Harimau,
Yes, it perhaps is a recruitment promo.
But given the idiosyncratic musicians of today, having a knowledgeable tech may improve matters, don't you think?
We have had awful sound settings in Blr recently. 90dBm plus levels, and often highly displeased audiences.

[varsha]

I wonder why retired AIR folks dont take up such consultant assignments . May be it is a question of priority . I remember the care Shanmukhananda sabha takes about these issues . They splurge a lot of money every 5-6 years and very senior guys in the pecking order are in charge of this department . Speaking from memory though .

[srikant1987]

There is possibly some ego problem too, for we find that some artistes' concerts are louder than is pleasant consistently, irrespective of the venue.

However I don't think that that can be squarely blamed for the shrieks we hear intermittently at some concerts.

Not content with that, we have singers saying, "Give me some sharp", or "Increase the bass", or dd some reverb".

Reverb is synthetic and I don't care much for it. You don't expect any "reverb", natural or electronically induced, practising in your home.

Sharp and bass are settings, however, are very real -- depending on the contents in a room, different frequencies are absorbed differently. In fact, freshly-bought music players themselves don't come with "neutral" settings, which means that there's tweaking done ALWAYS -- forget about presenting your "god-given voice".

In general, I feel that the best audio technicians are ones who "show up", and stay through the concert (themselves listening), being approachable to the artistes, organizers and audiences too. Not being able to see the equilizer and the technician typically is worrisome.

[Nick H]

harimau, the issue is not sound engineers attempting to improve on a poor voice, or poor artists asking that they should either fix, or replace quality with quantity, it is about sound engineers and their equipment ruining the best of voices.

Ego is an element in the matter, and part of the problem is that engineers should not take instructions from the stage for anything else but the monitor speakers.

Just maybe you've been listening to many wedding sound systems of late? It can be very bad for the aural health!

[vasanthakokilam]

part of the problem is that engineers should not take instructions from the stage for anything else but the monitor speakers.

I agree. It is sad that this issue keeps propping up as we saw in the couple of Bangalore concert reviews.

It was such a pleasant and considerate thing when Ravikiran actually did the opposite in the concert I attended couple of years back. He asked the audience how the sound level is. That was refreshing. I heard later that it was one of the things he does routinely and he does care about such things.

[uday_shankar]

It was such a pleasant and considerate thing when Ravikiran actually did the opposite in the concert I attended couple of years back. He asked the audience how the sound level is. That was refreshing. I heard later that it was one of the things he does routinely and he does care about such things.

The flip side of this is that in Chennai - and CM in general - I really believe that most rasikas have been habituated to such high levels of volume and the consequent distortion that it is considered the "normal". So invariably the request of for more, more and more volume.

[sureshvv]

And amplification seems to be doled out in proportion to seniority

[Nick H]

...and, sometimes, in inverse proportion to the size of the hall! :devil:

By the way, that article seems to be written by someone running a school for technicians and sounds like a recruitment advertisement.

Yes, but wasn't it also there that he does engineering for the Cleveland Crowd? In this instance I'm happy to let him get away with his advert: it's in a good cause. There should be sound-board licences, like driving licences, though it would probably only be necessary to turn everything up to full to get one!

[vasanthakokilam]

In this instance I'm happy to let him get away with his advert:

I agree with your general point. I am also scratching my head as to why Harimau is going out of his way to pick nits about a good thing.
May be he is blaming the reverb disease on the schools that train audio technicians.

I think even your 'let him get away' phrase is on the harsher side. I think the requirement should be full disclosure for such articles.
It is OK to encourage without reservation knowledgeable people in the field putting forth their ideas for the common good even if they are acting in their self interest and make a buck or two in the process.

Unsolicited rant ( not targeted at you ):
Self interest is after all what drives the world, not the selfless do-goodder idealism. That is not scalable however virtuous it is. That illusory good thing paradoxically stands in the ways of solving problems and solving them quickly. Not that I am against do-goodders.

[Nick H]

The disclosure is there ... which is how we know that he is running a school for this stuff. Indeed, I'm happy, and "getting away with it" was just a turn of phrase. My daily newspapers do worse ...daily.

[Rsachi]

To purchase Noise Thermometer posters, please contact the Sight and Hearing Association
directly at 800-992-0424 or on the web at www.sightandhearing.org.

CM in concert halls routinely touches 80 dB(A).

[mohan]

He asked the audience how the sound level is. That was refreshing. I heard later that it was one of the things he does routinely and he does care about such things.

I cringe when I hear artistes ask the audience this in concerts.

In concerts I have organised we would have completed a full sound check going for 45 minutes. We have a professional sound technician balancing the sound and various sabha volunteers stationed around the auditorium to monitor the sound levels. Then as the concert goes on the main artist asks the audience 'how is the sound?'. Some people say shake their head, some nod, some do the puzzling Indian shake of the head which could mean yes or no. Some deaf mama in the mama in the seventh row wants more sound. Some mami wants it all softer since she arrived late and is now sitting right in front of the speaker. The smart audio technician will just pretend to make some adjustments and not change a thing, backing his own skills.

If artistes care about such things, they should insist on a full and proper sound check before the concert and leave the rest to the audio technician and the organisers.

[Rsachi]

Mohan,
We think alike: mike mess

[vasanthakokilam]

Mohan: Though you quoted my line to post a contrary opinion, I very much agree with what you wrote there. That is a different dimension and obviously if what you state is actually what happens, the problem is solved.

But in some venues, that is not what seems to happen. The Vocalist and the violinist can not hear properly on the stage and so they signal the audio guy to increase it. The mridangist would do the same. They do not have an iota of an idea how it is for the audience. So my comment was in that sense. It was good to see the artist inquiring how things are. If things are really loud and there is an unmistakable 'feedback' from the audience that things are too loud, something can be done about it, instead of suffering through it like what the reviews suggest. When Ravikiran asked, the manner of it was like asking how the food is (uppu-urappellam sariya irukka - even though you may have tasted it and made sure the salt and spice levels are good). Yeah, if only one or two say something, the tactic of the smart audio technician ( and the smart cook ) is the right one

[Nick H]

Mohan, yes, but with a but...

The first but is that sound in a full hall is not the same as sound in an empty hall, so however thorough your pre-concert sound check is, it can only go part of the way in establishing the correct settings. I am sure, though, that given the professional manner in which you are going about presenting the concert, you are aware of this.

The second is that I don't feel that the performers, especially vocalists, sing properly during a sound check. They hum a bit, and mutter a few melodic lines, then, when they have someone to sing to, they warm up and the howling feedback starts! Again, I'm sure that you are aware of this one.

The last is ... ok, your pro has done their job, and probably done it better than most, but there is no harm in checking, and the proof of the pudding is in the eating --- eating with the ears in this case --- and that is done by the audience.

When Nick calls out that he wants to hear the morsing (I did once respond to Ravikiran with the information that the mridangam was too low. Unusual, but true, and he took it on board) or the tambura player's grand mother only wants to hear the tambura, then the remedy is exactly what you suggest, and is the same as when requests from the stage will spoil the house sound --- symbolic knob twiddling!

To purchase Noise Thermometer posters, please contact the Sight and Hearing Association
directly at 800-992-0424 or on the web at www.sightandhearing.org.

And you can get SPL (Sound Pressure Level) apps for your android (probably iphone too) phone easily. Whilst they should be calibrated against a real SPL meter for accurate results, for our purposes they are good enough uncalibrated. Technology has invaded to the point where I now see grandmothers sitting with iPads on their laps (hey, some of them might even be retired IT directors!) and I think we can easily get used to using this sort of tool. Android Sound Meter comes with a nice table that relates those dB numbers to real life. It's free. There's a pro version at small cost that has one or two extra facilities.

The day will come when some sound engineers find these things being thrust under their noses!

Until then a little cotton wool in the ears reduces the dB without too much sound degradation.

[vasanthakokilam]

Rsachi, Nick:
Feeling a bit lazy to track this down myself and I thought I will take the liberty to ask you two instead.

I see Dbs mentioned as both positive and negative numbers. Can you two straighten me out on that? I see these kinds of positive numbers and the common notion that 20dB is too low for humans to hear and above 80-100 can be too loud and harmful. This is what I typically go by and interpret it as a measure of the loudness of the sound ( amplitude or power of the sound ).

I also see, in more technically oriented articles, where the dBs are negative . I will try to find some example references.

What is the relationship or connection between the two? Is one number convertible to the other ( like F and C for temperature )?

[mahavishnu]

VK: It is based on a logarithmic scale (used on a ratio of the a said sound to a reference) and hence the differences in intensities you see are not linear.
You will find a very nice explanation with sound samples here: http://www.animations.physics.unsw.edu.au/jw/dB.htm. You will only get negative values in dB when the value of the measured sound is lower than its reference. (as is log of a number < 1)

The unit itself was named for Sri Alexander Graham Bell (hence Bel) but the decibel is more popular because of the ecology of its use in standard human listening environments.

Here is some recent work from my lab on why one tends to speak louder in a noisy environment. It is called the "Lombard" effect. I'm sure all of us have experienced this effect when we listen to music with headphones on. http://www.plosone.org/article/info%3Ad ... ne.0049370

[vasanthakokilam]

Mahavishnu: Thanks. That straightens me out. The section under 'Standard reference levels ("absolute" sound level)' for sound is what I was confused about. Now it is clear for sound in the hearing context.

So, are there different reference levels for different things ( like sound having one standard reference level ) and so we have to be mindful of when dB is used, we need to be careful about what the usage is and what the corresponding reference level is? I am also implicitly assuming that negative dBs for sound in audio/hearing contexts do not have much practical meaning ( though it is still theoretically possible even if no one can hear ).

I will check out the work from your lab. Thanks.

[Nick H]

When you shout at me, the dB are negative. When I shout at you, they are positive.

] ]

But seriously... I often admit to my failings on the maths front, and I do find this stuff difficult. Much better explained by Uday, Mahavishnu, and such people, who actually know the science and maths and can put it across.

However, in practice I observe two kinds of dB measurement, one of which is always positive, and one of which [should be] always negative.

When measuring sound levels, positive numbers are given, and people say things like, "50dB is the sound level of a quiet street." There is no upper limit, because even an atomic explosion would be measurable.

When handling digital recording, there is an upper limit, because there is a maximum number of bits that can be used for each sample. This cannot be exceeded, and is stated as 0dB, with lesser quantities being given negative numbers. People say things like, "do not let your recording exceed -1. or even -5 dB," (where -1 is "louder" than -5) If your recording does exceed 0dB, you just record a horrid noise, which is called clipping. These numbers only relate to actual playback relative to each other. Actual playback volume is still controlled by the knob on the amp.

This is an innumerate layman's explanation. Logs, to me, are what you burn in the winter.

There is some great stuff on that physics site. Try the Music Acoustics FAQs. Another of my favourite practical tests sites is audiocheck.net

[Rsachi]

VK: Mahavishnu's links are great for an understanding.
Since dB is a log ratio, as long as we compare two sound levels in dB(A) against the same reference, we can start to define what is too loud. I have successfully used my iPad/iPhone app called dB Pro to measure loudness of medical operation room equipment in relative terms! Here is a screenshot in my bed just now (red arrow shows current reading):


So we can summarize this thread as follows:
1. Sound levels have to be monitored throughout a concert properly for audience listening comfort and pleasure.
2. Sound checks and calibrated stage monitors will ensure artistes and audiences experience loudness the same way.
3. Sporadic loudness adjustments, poorly set mikes/contact mikes, poorly placed speakers, poorly set monitors, individual musician demands, can all add to poor sound adjustments and destroy the concert experience.
4. The sound techs need training.
The rest of discussions here simply amplified/added texture to the discussion. That's it in my view.

[vasanthakokilam]

Nick: I think the negative dB values used in such recording contexts is probably what I had in mind when I posed the question. Given mahavishnu's explanation & link and your example case where negative dBs are used, it seems to be that in different contexts the reference level chosen are indeed different.
In all cases the dB is actually a ratio. When we say 'attenuate the sound by 1 dB' that is a usage where the reference level does not apply since it is talking about reducing something by a ratio. When we talk about cases where it is an absolute value ( sort of a contradiction ), then the unstated standard reference level is important. It looks like they are different in those two contexts that you mention. May be, in other engineering contexts where power or pressure of an entirely different thing is expressed, the reference level is different and so a dB magnitude has to be properly interpreted. I am just making this up, so curious if there are different reference levels in different disciplines. A confusing maze indeed ( rivaling our gathi vs naDai confusions )

[vasanthakokilam]

Rsachi: Yes, understood. Those are general principles to follow. To actually do it and know what one is doing, it does require training as you say and hopefully that is what is taught and a practice evolves that is specific to CM given its unique stage setup with main artist, violinist, mridangam, upapakkavadyam and tampura.. One thing I like about CM studio recordings is that the mix is usually very good, at least the modern ones. I have Sanjay's studio recording of 'Brochevare..' ( Sri Ranjani ). It is a total freak out by him and the mridangist and mix is just right for that kind of playing. Listening to it in the enclosed confines of a car with good bass response audio system is an awesome experience. The same freak out in a concert might not be so pleasing to the ears, especially if audio levels are not set up properly.

May be, Sanjay can try to reproduce that effect at his Music Academy concert if it happens to be the same Mridangist. The MA audio systems may hold up to that and it will be a good song to play in that manner around the half hour to 45 minute mark.

When you used 'Medical Operating Room equipment' and 'your bed' in the same breath, I first thought you are now in bed at an operation room. No, right?

[Rsachi]

My iPad's right now operational in bed too, but 2 years ago, I had a big medical equipment that had to be put to sleep to make it quiet. The sound level it produced when running at 65 dBA was well below the level in a Carnatic concert today, but was considered a bit loud for a medical equipment room. So!

[vasanthakokilam]

Let me circle back to this topic and provide a summary. The site that Mahavishnu and Nick provided pretty much has all the info. They have also explained it already in their words. This is just another summary in my words, nothing new.

Thinking this through, my question arose from the following 'dissonance'. If I look at a sound spectrograph, I see negative dB numbers like -70dB. On the other hand, In the 'audio context' we normally talk about 70 dB as loud sound. So what is going on?

There are indeed two different reference levels and two different scales. The reference level is needs to be mentioned along with the numbers but sometimes it is not.That itself is enough to cause confusion. Adding to that, there can be negative dB values in both scales. And obviously they are not the same.

Since I understand it now, I thought I will provide a brief summary in case it is beneficial to others. For authoritative answers please go to the links in the previous posts provided by Mahavishnu and Nick.

1) Sound pressure levels as used in this commonly used graph.


This is the context used in this thread. They are usually given in positive values. A high positive value means high volume sound.
0 dB in that context is a very faint sound ( and not zero sound ). Theoretially, you can have negative dB values. That means sound levels that are even below the reference level.

This dB should be properly marked as dB SPL but people often omit the SPL ( but not in the graph above )

2) The db levels shown in a spectrograph as in this picture. This is a different scale and the dB values are negative.



Here the reference level of 0dB is the maximum sound level. So negative dB values in this context do not mean the faintest of sound but just refers to sounds that are below the maximum. This context is also the one used in recording equipment, meters, audio consoles etc.

This dB should be marked dBV but very often this is left out ( as in the above graph )

Now, can you convert between the two? That was one of my questions. The http://www.animations.physics.unsw.edu.au/jw/dB.htm site says there is no simple way and why.

"....How to convert dBV into dB of sound level? There is no simple way. It depends on how you convert the electrical power into sound power. Even if your electrical signal is connected directly to a loudspeaker, the conversion will depend on the efficiency and impedance of your loudspeaker. And of course there may be a power amplifier, and various acoustic complications between where you measure the dBV on the mixing desk and where your ears are in the sound field...."

All clear now? Not but just that much less foggier!

I think some of the issues in this thread ( fixing audio levels in an auditorium ) are indeed indirectly caused by this fundamental difficulty in converting between dBV and dB SPL. The audio guy twiddles some knobs that may be marked in dBs (dBV) where as people sitting in the room are experiencing the sound with dBs of the first context (dB SPL). Since the conversion is not straightforward and depends on so many factors, what Rsachi does with the iPad application is the way to go. Adjust dBV by twiddling the knobs audio console and check the dB SPL displayed by the iPad application at a few places in the auditorium.

[mahavishnu]

Nicely summarized, VK.