Audio recording

class: center, middle, inverse, title-slide

# Audio recording
## 710 | Week 6
### Bradley McDonnell
### 2022/02/14 (updated: 2022-02-14)

---

# What is sound?

Sound is waves of pressure in the air:

![](img/wave.gif)

[source](http://bentibbetts.net/wp/?p=8772)

---

# What is sound?

.pull-left[**Sound is like waves in the ocean:**
- High vs. low pitch = frequent vs. infrequent waves
  - Frequency of a sound wave
- Loud vs. quiet = height of the wave
  - Volume, Amplitude, or Intensity 
- Loud vs. quiet = closer or farther
]

.pull-right[
![](img/surf.gif)
]

---
# What is sound?

[What is sound?](https://youtu.be/hfzCLClVO8g)

???

Don't play in class

---

# Keys for audio recording

Frequency in Hertz (Hz) or Kilohertz (kHz)
 - 1,000 Hz = 1kHz

Intensity/amplitude/volume in decibels (dB)
  - Humans hear between 20Hz and 20,000Hz
  - Microphones should be around the same range!

---

# Hearing with our ears

[Description of hearing](https://youtu.be/T8lKKlnnC6M)

1. Air pressure vibrates eardrum 
2. Translated into electrical impulses
3. Electrical impulses sent to the brain

???

Don't play in class

---

# Hearing with a microphone
 
<iframe width="560" height="315" src="https://www.youtube.com/embed/PE6Qn4ZiEyo?start=17" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

[Introducing microphones video](https://youtu.be/PE6Qn4ZiEyo)

???

Play in class until 2:40 after polar patterns

---

# Hearing with a microphone

- Dynamic and condenser
- The anatomy of microphones
  - Phantom power
  - Transducer (sound wave > electrical energy)
  - Microphone Diaphragm
- Frequency response
- Polar patterns

---

# Dynamic vs. condensor microphones

.pull-left[**Dynamic**
- Rugged
- No extra power
- Not sensitive
]

.pull-right[
**Condenser**
- Delicate
- Extra power needed
  - Battery, phantom power (see below)
- Very sensitive
]

---

# Dynamic vs. condensor microphones

[Dynamic vs. Condensor Microphone](https://youtu.be/Mxp3eCCQyas?t=1m19s)

???

Don't play in class

---

# Dynamic microphones

### Which type of microphone do documentary linguists want?

---

# Frequency response

[Frequency response tutorial](https://youtu.be/7TH82dx7Qas?t=14s)

### Key concept: Flat vs. Roll off

???

Play in class until 2:40

---

# Polar patterns

[Polar pattern tutorial](https://youtu.be/rYWnSuAxato?t=22s)

See: [additional tutorial on polar pattern](https://youtu.be/0cj18EQQAm8)

---

# Polar patterns

- Omndirectional
- Unidirectional
  - Cardioid
  - Super-cardioid
- Bidirectional

**What about polar patterns in stereo microphones?**

---

# Electrical output

[Micorphone specifications](https://youtu.be/UYMaRhRt8Ts?t=10s)
- Balanced output
  - [XLR vs.  1/4"  vs. 3.5mm](https://youtu.be/ZAKhh8wpXDE?t=19s)
    - XLR pins (3, 5, 6, 7)
    - Balanced vs. unbalanced
    - TS vs. TRS

- Microphone pad
- Phantom power

[Long explanation of reasons for using  XLR](https://youtu.be/Z5ElNzY5e1I?t=50)
---
class: center, middle, inverse

# Hearing is NOT listening

---

# Hearing is NOT listening

Cocktail party effect
<iframe width="560" height="315" src="https://www.youtube.com/embed/iO3jTl0WuS4?rel=0&amp;showinfo=0&amp;start=3" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen>
</iframe>

[Cocktail party effect](https://youtu.be/iO3jTl0WuS4?t=3s)

An example

???

Play first 55 seconds

---

# Hearing is NOT listening

- Ears only hear, brains listen
- Mics don't have brains

**Documentary linguists need to be the brain!**

---

# Two ears, one brain

One ear = mono

Two ears (like a mouse) = stereo

### 🎧 Listen with headphones 🎧

Two ears (like a human) = binaural/ORTF
 - Organisme Francais de Radiodiffusion et de Television
 - Volume differences across two cardioid mics at 110 degrees 
 - Timing differences at 17cm apart

---

# Two ears, one brain

### Compare...

### 🎧 Listen with headphones 🎧

---

# Binaural vs. stereo example

Binaural vs. stereo
<iframe width="560" height="315" src="https://www.youtube.com/embed/5KSMASKjwUI?rel=0&amp;showinfo=0&amp;start=8" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

### 🎧 Listen with headphones 🎧

???

Don't play in class

---

# Interem summary and advice

.pull-left[
Recordings can be:

- Mono
- Stereo
- Binaural
]

.pull-right[
Microphones have directionality:

- Omnidirectional
- Unidirectional
  - Cardioid
  - Super-cardiod
- Bidirectional
]
---
class: inverse

# Advice

When in doubt choose...

1. a **stereo** microphone (cardioid) with an *audio recorder*
2. a **shotgun** microphone (super-cardiodi) with a *video recorder*

---

# Reputuable brands for microphones

1. AKG
2. Audio-Technica
3. Rode
4. Sennheiser
5. Shure
6. ...

---

# Using microphones for the best quality

1. Monitor recordings
2. Maintain a good *signal to noise ratio*
3. Microphone placement
4. Minimize background noise

---

# Monitor recordings
.pull-left[
![alt text](img/monitoring.png)
]

.pull-right[
- Monitor recordings (as much as possible)
  - But *don't* continuously adjust sound levels
  - It's okay to peak when sound is loud
]

---

# Audio issues

- Keep sound levels from -20dB to -12dB
  - see *Shut Up and Shoot*, p. 196-197

No clipping

Clipping

---

# Signal to noise ratio

- Background noise is inevitable, but keep it at a minimum
- 10:1 = language is ten times as loud as background noise 
- 1:1 = language is as loud as background noise

---

# Signal to noise ratio

A good signal to noise ratio can be acheived by considering...
- Microphone placement
- External noise (road noise, rain)
- Room acoustics

*Which recording has the better sound quality?*

---

# Microphone placement

Maximize signal...
- Place microphone as close as possible
  - Microphone shouldn't be closer than 7-8 inches from speaker's mouth
  - Position headworn microphones to the side of the mouth
      - Read microphone instruction manual
  - In recording groups, consider the polar pattern
      - Move microphone closer to soft-spoken speakers

---

# Handling noise

**Avoid handling noise!**

### ‼️ Use cradles and mic stands
  
  - Not uncommon for people to touch microphone or play with table

---

# Room acoustics

.pull-left[
<iframe width="560" height="315" src="https://www.youtube.com/embed/cp56A6TcL1E" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

[Bad room acoustics](https://youtu.be/cp56A6TcL1E?t=1s)
]

.pull-right[
<iframe width="560" height="315" src="https://www.youtube.com/embed/cp56A6TcL1E?start=95" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

[Better room acoustics](https://youtu.be/cp56A6TcL1E?t=1m35s)
]

- Sound waves bounce or rooms with lots of hard surfaces
- Dampen sound waves by using blankets, rugs, mattresses

---

# Sources of noise

- Wind
  - Use a windshield (e.g., deadcat)
- Traffic, rivers, generators
  - Record at a different time
  - Use polar patterns to your advantange
- Poor room acoustics
  - Use rugs, mattresses, blankets to dampen sound

---

# Sources of noise

- Fans, electronics, refrigerators
  - Turn off, Unplug (for a bit), move (if possible)
- Noise from participants or neighbors
  - Direct people elsewhere (if possible), 
  - include them in on the recording

### ‼️ It's important to work with trusted community members to help you ensure the best quality audio!**

---

# Audio problems

Can you spot the audio problems?

‼️ Turn sound low for this first example!

---

# Recorders

Solid state recorders with XLR inputs:
 - Good place to purchase: <https://www.bhphotovideo.com>
   - [Zoom H4n $299](https://www.bhphotovideo.com/c/product/1253811-REG/zoom_h4npro_4_channel_handy_recorder.html?sts=pi)
   - [Tascam DR100MKIII $399](https://www.bhphotovideo.com/c/product/1263849-REG/tascam_dr_100mkiii_linear_pcm_recorder.html)
   - ...

---

# Sampling rate

![alt text](img/sampling-frequency.gif)

---

# Sampling rate

- 44.1 kHz or more
- Typically stereo
  - Maybe mono
- 16 bit or more

---

# Sampling rate differences
.pull-left[
- Sampling rate 44.1kHz 
<audio controls>
<source src="audio/sampling-44-1.wav" type="audio/wav">
</audio>

- Sampling rate 22.05kHz 
<audio controls>
<source src="audio/sampling-22-05.wav" type="audio/wav">
</audio>

- Sampling rate 11.125kHz
<audio controls>
<source src="audio/sampling-11-025.wav" type="audio/wav">
</audio>
]
.pull-right[
- Sampling rate 5.5125kHz 
<audio controls>
<source src="audio/sampling-5-5125.wav" type="audio/wav">
</audio>

- Sampling rate 4kHz 
<audio controls>
<source src="audio/sampling-4.wav" type="audio/wav">
</audio>

]
---

# Basic audio setup

  
  - [Tascam DR100MKIII $399](https://www.bhphotovideo.com/c/product/1263849-REG/tascam_dr_100mkiii_linear_pcm_recorder.html)
  - [Audio-Technica Stereo Microphone $249 ](https://www.bhphotovideo.com/c/product/761016-REG/Audio_Technica_AT2022_AT2022_X_Y_Stereo_Microphone.html)
  - [Stereo XLR cable $24.95](https://www.bhphotovideo.com/c/product/994801-REG/rode_nt4_dxlr_cable_5_pin_stereo_xlr_cable.html)
  - [Panasonic eneloop pro charger & batteries $52.99](https://www.bhphotovideo.com/c/product/1258154-REG/panasonic_k_kj17khc82a_eneloop_pro_high_capacity.html)
  - [(2) SanDisk 16GB $21.94](https://www.bhphotovideo.com/c/product/1182600-REG/sandisk_sdsdxne_016g_gnci2_extreme_16gb_sdhc_u3.html)
  - [Sony closed-back headphones $79.99](https://www.bhphotovideo.com/c/product/49510-REG/Sony_MDR_7506_MDR_7506_Headphone.html?sts=pi)
   
   **Total = 827.87**