A Quick Look at Decibels - RSD Academy

I’ve been busy revising my textbook on Analog Circuits and putting it online at RSD Academy. The pages I just uploaded are a math review on exponents and logarithms and decibels. Here are the links to the pages.

Exponents and Logarithms:




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39 thoughts on “A Quick Look at Decibels – RSD Academy”
  1. Dear Bob, I watched a few videos on this subject before I found this one. They made me nervous and made me click away. Your calm speaking style is such a relief and allows the listener to concentrate on the content that is so easily explained here. Thank you very much !

  2. I usually don't write comments but just wanted to say that this really helps. And your voice is so calming that I don't want this video to be over.

  3. There is danger of high frequencies (ionization); is there danger of the power behind the frequency? Can I compare the relationship of frequency/power to current/voltage? – it's the current that is dangerous, not the voltage.

    I'm trying to think about radio frequency permeability thru mass , like a wall. I heard that high frequency 5G does not permeate matter, even a leaf – but I believe that 5G is low amplitude (low power/low watts) – Is AM and FM frequencies more permeable thru walls because they are broadcast at higher amplitude (power) – would a high frequency at a low power have the same permeability as a low frequency at high power? – Why do high frequencies ionize if not by virtue of increased frequency (above the EMF spectrum of non- ionizing frequencies? – their may be other factors other that total energy at play such as reflection/diffraction or whatever.

    If dropping 2 rocks into a pond from the same height inside a vacuum – how does a small rock spinning at 200MHz (200 million rotations per second) compared to a larger rock not spinning at all – Could they have the same energy? Same or different permeability? Then how can a high frequency' with low amplitude and rapid cycles per second compared to a low frequency of a higher amplitude but lower cycles per second? Could they have the same energy? Same or different permeability?

    rock is spinning to represent EMF frequency – rock that is not spinning – I should have said spinning slower than the small rock but is heavier (amplitude / weight — frequency / spin rate) – does both an increase in frequency and an increase in amplitude factor into total energy?

  4. Great video – but isn't Wi-Fi measured by negative dB? Negative decibel in this case meaning that ratio of things in log10 is less than 1. And Unit is W/m^2 if memory serves. Long time ago I managed to do 1 semester of mechatronics… ehhhh where would I be if I didn't have to drop out?

  5. I'm going to be honest. This didn't really help me much. I wanted to go over the concept of 10 log(x/y) but you completely skipped over that. I get the concept of 3dB is doubling and so on. But I am trying to study for a test and granted, I could probably memorize the answers given in the book since it will most certainly be the same question/answer on the test, i would like to use the 10 log(x/y) for power ratios and 20log(x/y) voltage ratio in real life. basically want to see someone work out the math on those and no one seems to be doing so. makes me wonder if anyone even knows how to do the math on those logarithms.

  6. Good day sir,,thank for this video,,,I have a question,,,,so if I reduce my gain negative 3 db with a spl sensitivity of 132 1watt per meter,,I will get a 116 db????

  7. Fascinating, i now know what that log button on my calculator is used for and a very good explanation as always

  8. GOSH I WISH I COULD GIVE THIS MAN A BIG OL HUG. Cripes, I've been through video after video about "scorpion tail" methods, mumbling script-less "math tutors" and countless "use this method to get this right on a test" approaches. Not once has anyone even attempted to cover functional application or comprehension. I am subbing so hard.

  9. So I'm an Electrical Engineer believe it or not and never really used decibels that often. I finally got a job where I'm working in RF and audio and this had to be the best explanation on understanding it. Many videos out there use common examples of the normal scales, but you explain it using numbers like 7dB or 15dB something odd, which trust me clears everything up so well for me now. Thanks! 🙂

  10. Great video and link to your notes. Many people provide misleading info in relation to volatge and power, your information makes the subject of Decibels clear and complete

  11. Did you say we can hear up to 1 hundred million Pascals? And on the graphic is it a billion? Lol that's pretty loud.

  12. Not to be a stickler here teach, but wouldn't 20upa TECHNICALLY be .2dB? That just not common place? Or am I mistaken? Can it not be referred to as .2dB because it's the base measurement for it? Besides that awesome video as always thanks.

  13. This is clearly the best explanation of how decibels work. Thank you very much for this valuable lesson.

  14. I believe a power ratio is 20 Log (ratio) and voltage ratio is 10 Log (ratio)

    Update: Oops! I had them reversed!

  15. প্রণাম নিবেন স্যার, চমৎকার ভিডিও। Motor এ snubber এর ব্যবহার নিয়ে একটা ভিডিও করলে খুব কৃতজ্ঞ হব।

  16. Very nice explanation. To be complete maybe is missing some short explanation about dbm dbu etc…thanks for your altruism to help people to understand easily complicated thinks!

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