Hertz and frequency response

Video: Hertz and frequency response

Now one unit of measurement we should talk about is Hertz. It shows up all over the place when we are dealing with audio. So the sooner we take a look at it, the better. The best way to think of hertz is that it represents the number of times an event is completed per second, or the number of cycles per second. It represents different things in different situations, but it always refers to a certain amount of events per second. Now the two places you will find in dealing with audio very commonly are with frequency, or pitch, and also with sample rates.

Hertz and frequency response

Now one unit of measurement we should talk about is Hertz. It shows up all over the place when we are dealing with audio. So the sooner we take a look at it, the better. The best way to think of hertz is that it represents the number of times an event is completed per second, or the number of cycles per second. It represents different things in different situations, but it always refers to a certain amount of events per second. Now the two places you will find in dealing with audio very commonly are with frequency, or pitch, and also with sample rates.

Hertz is represented by a large H and a little z, and then a few prefixes. For instance, in our chart, we have 1 Hz or one cycle per second, 1 KHz or 1000 cycles per second, 1 MHz or 1,000,000 cycles per second, and 1 GHz, 1 thousand million cycles per second. Let's talk about how hertz relate to frequency next. When we talk about hertz in relationship to the frequency of the sound, we are talking about the number of times a sound wave completes a cycle per second, the higher the frequency, the higher the pitch, so let's look at these graphics.

First we have a complete cycle of the Sine wave. On the left, we have it in a linear display, and on the right, I've slid the bottom half around just to illustrate that a cycle means a complete revolution, or once around, so to speak. Down below, we have several different frequencies and their Sine waves. On the left we have the frequency, and in the middle we have one cycle of that frequency. Then on the far right here we have all three frequencies against the same amount of time. Now you can see that the higher the frequency, the shorter the cycle and therefore, the more cycles that take place per second.

Now we can see that there are quite a few more cycles per second at 6 KHz, than at 1 KHz. So again, frequency refers to the number of times a sound wave completes a cycle. Now let's look at what we call the range of human hearing. The human ear is capable of hearing frequencies that range from the very low pitched, 20 Hz to the very high-pitched 20 KHz, or 20 to 20K. Sounds that exists above this range are referred to as ultrasonic and those that are below are considered subsonic.

Now in audio production, we tend only to concern ourselves with the human range of hearing, this 20 to 20K range. Now if you are making music for dolphins or doing a podcast for bats, you would want to include frequencies all the way up to 200 KHz, because they can actually hear that high. But humans, perhaps like you, and I, can't hear beyond 20 KHz. So that's what we tend to worry about. Now when we work with audio, we tend to break this range down even a little bit further to kind of simplify things into three sub-categories, we call them the lows, the mids, and the highs.

And as you would expect, the lows refer to the lower frequencies, the mids to the mid ranged frequencies, and the highs to the higher frequencies. A little side note on the range of human hearing, most of us don't hear that much above 16 KHz even though the range goes up to 20K, and actually as we get older, we hear even less than that, which is why kids can set their cell phones to ring with these really high pitched ring tones, and when they go off in class, the teachers can't hear it, because their hearing is not as good as it used to be--and everyone says kids are stupid.

And that provides a pretty nice segue into talking about frequency response. Frequency response generally refers to how sensitive a person or a microphone or a device is to different frequencies. This is often represented in a graph, and it's well-worth understanding because you are going to come into contact with this quite a bit when you look at different specs for gear and equipment. What the graph will show is the frequencies along the X-axis and then the response to those frequencies or the sensitivity along the Y-axis.

So this top chart shows a flat frequency response. Now in other words, it represents equal sensitivity to all frequencies. And when it comes to audio recording equipment like microphones and speakers, a flat or accurate response is very favorable, because it can help us achieve accurate representations of the sound. But in reality, humans and very often devices, don't actually have flat accurate frequencies responses. It's actually quite difficult to manufacture a device with a flat frequency response. So below, we have a chart showing an uneven frequency response.

In other words, it shows different sensitivities to different frequencies. And this is much more like what our frequency response probably looks like as humans. We are a little more sensitive to some of the frequencies here around the 8K range, and then we have quite a drop-off in sensitivity when it comes to the extremes of the range of human hearing. So that's basically it for hertz, frequencies, the range of human hearing, and frequency response. To recap, hertz, which is signified by a big H and a little z, refers to the number of times a cycle or something happens per second.

When we talk about hertz in relationship to frequency, we are talking about the number of times a sound wave completes a cycle per second. The range of human hearing is a frequency range of 20 Hz at the low end, up to 20 KHz at the high end. And finally, frequency response refers to the range of frequencies a person can hear and how sensitive they are to those frequencies, and we can use charts to represents the frequency response of different things such as speakers, microphones, people, dolphins, bats, wombats, you name it.

Next, we will talk about phase.

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This video is part of

Digital Audio Principles

110 video lessons · 26795 viewers

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50s
1. Welcome
50s
2. 1. Sound and Digital Audio

39m 10s
1. What is sound?
4m 15s
2. Hertz and frequency response
5m 34s
3. Phase
2m 39s
4. Capturing audio
3m 39s
5. Sample rate
6m 16s
6. Bit depth
9m 47s
7. The waveform
5m 3s
8. Audio file formats
1m 57s
3. 2. Digital Audio Workstations

7m 25s
1. What is a digital audio workstation?
2m 59s
2. Typical DAW signal flow
4m 26s
4. 3. Microphones

50m 33s
1. What microphones do
1m 57s
2. Element types
5m 0s
3. Pickup patterns
6m 51s
4. Axis
2m 52s
5. Frequency response and the proximity effect
5m 10s
6. Phase issues
1m 41s
7. Microphone types
8m 44s
8. Miking vocals
5m 39s
9. Miking amplifiers
2m 17s
10. Miking drums
10m 22s
5. 4. Cables and Connectors

16m 39s
1. Cables and connectors overview
2m 42s
2. Balanced and unbalanced cables
3m 19s
3. Common cable types
7m 13s
4. Cable tips
3m 25s
6. 5. Audio Input/Output Devices

12m 16s
1. What is an I/O device?
1m 41s
2. Analog to digital conversion
3m 10s
3. Tour of an audio interface
4m 49s
4. Interface considerations
2m 36s
7. 6. Input Levels and Preamplifiers

21m 5s
1. What is a preamp?
3m 21s
2. Input levels
5m 29s
2m 18s
4. Phantom power
2m 37s
5. Phase reverse
3m 4s
6. Preamp demo
4m 16s
8. 7. The Mixer

12m 56s
1. What is a mixer?
5m 55s
2. Input section
1m 17s
3. Channel strips
3m 16s
4. Master section
2m 28s
9. 8. Monitoring

18m 21s
1. What is monitoring?
2m 11s
2. Speakers
4m 47s
3. Room considerations
5m 43s
3m 50s
5. Monitoring levels
1m 50s
10. 9. Computers and Audio

15m 23s
1. What role do computers play?
1m 36s
2. Performance issues
4m 11s
3. Hard drives
4m 38s
4. Mechanical noise
2m 10s
5. Authorization
2m 48s
11. 10. Setting Up for Recording

6m 54s
1. Planning for recording
54s
2. Doing a system check
1m 26s
1m 42s
4. The recording environment
2m 52s
12. 11. Digital Audio Software

25m 52s
1. Types of digital audio software
38s
2. Multi-track recorders/sequencers
4m 56s
3. Two-track recorders/waveform editors
4m 55s
4. Loop-based music production software
5m 44s
5. Plug-ins
6m 56s
6. Other varieties
2m 43s
13. 12. Common DAW Components

18m 59s
1. Common components
46s
2. The transport
2m 4s
3. The toolbar
3m 19s
4. The Edit/Arrange window
4m 42s
5. The mixer
5m 8s
6. The file list
3m 0s
14. 13. Recording and Playback

19m 17s
1. Setting up a session
3m 30s
2. Assigning inputs and getting signals
3m 19s
3. Input modes
3m 28s
4. Overdubbing and punching
5m 14s
5. Bouncing down
3m 46s
15. 14. Editing

19m 42s
1. What is editing?
1m 21s
2. Waveforms
2m 53s
3. Making silent cuts and trims
7m 1s
8m 27s
16. 15. Plug-ins

1h 23m
1. What are plug-ins?
3m 0s
2. Using plug-ins
6m 11s
3. EQs
7m 4s
4. Dynamics pt. 1: Compressors, limiters, expanders, and gates
5m 40s
5. Dynamics pt 2: Applying dynamic effects
7m 2s
6. Pitch shifting
6m 14s
7. Reverb
9m 28s
8. Echo and delay
6m 23s
9. Modulation effects: Phaser, flanger, and chorus
9m 39s
10. Sound tools pt. 1: About, gain, normalize
7m 39s
11. Sound tools pt. 2: Reverse and time compression/expansion
6m 29s
12. Sound tools pt. 3: Noise reducers, dither
8m 11s
17. 16. MIDI

23m 43s
1. What is MIDI?
3m 6s
2. Keyboard controllers
1m 23s
3. Computer-based virtual instruments
1m 6s
4. Control surfaces
1m 6s
5. Recording and editing MIDI
12m 4s
6. Virtual instruments
4m 58s
18. 17. Mixing

27m 29s
1. What is mixing?
1m 54s
2. Some common objectives
3m 4s
3. Some useful techniques
5m 59s
4. A quick mixing demo
16m 32s
19. 18. Mastering

18m 48s
1. What is mastering?
2m 24s
2. Sonic maximization
9m 43s
3. Final preparations and exporting
6m 41s
20. 19. Audio File Compression

13m 34s
1. What is audio compression?
2m 16s
2. Popular formats
2m 9s
3. Bit rate, sample rate, and channels
5m 42s
3m 27s
21. 20. Voice Recording

15m 6s
1. Essential gear
7m 36s
2. Voice recording setups
1m 43s
3. The voice production process
5m 47s
22. 21. Digital Audio Debates

10m 4s
1. Analog vs. digital
2m 48s
2. Tube vs. solid state
5m 6s
2m 10s

18s
1. Goodbye
18s

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