2. Listen

2. Listen #

Exercise 2 indoor soundwalk #

  • Soundwalk in the school.

Listen vs Hear #

What is the difference?

Analog vs digital. Continuous vs discrete. #

https://www.audiocruiser.com/analog-and-digital-sound/

  • Is nature analog, digital or hybrid system?
  • Paradoxes of Zeno
  • Digital philosphly & Konrad Zuse

Sample rate & bit depth #

The sample rate in digital audio refers to the number of times per second (per second) that a sound is sampled when it is converted from analog to digital format. Essentially, it’s the frequency at which the analog signal is measured to create a digital representation.

Here’s how it works:

  • Analog to Digital Conversion (ADC): An analog audio signal (like the sound captured by a microphone) is an electrical representation of sound waves. To convert this continuous signal into a digital form that a computer can understand, it’s necessary to take precise measurements of the signal at regular intervals. This process is known as sampling.

  • Sample Rate: The sample rate is measured in Hertz (Hz), which is the same as samples per second. Common sample rates include 44.1 kHz (used for CDs), 48 kHz (common in video production), 96 kHz, and even 192 kHz for high-resolution audio.

  • Nyquist Theorem: According to the Nyquist theorem, the sample rate should be at least twice the highest frequency contained in the audio signal to accurately reconstruct the original sound. For example, since human hearing ranges up to about 20 kHz, a sample rate of 44.1 kHz is sufficient to capture all the detail that humans can hear.

  • Bit Depth: In addition to the sample rate, the bit depth determines the resolution of each sample. While the sample rate refers to the ‘width’ of the digital audio (how many times per second it’s sampled), the bit depth refers to the ‘depth’ (how many possible values each sample can have).

The higher the sample rate (and the higher the bit depth), the higher the quality of the digital audio. However, higher sample rates and bit depths also mean larger file sizes. Therefore, it’s important to find a balance between audio quality and file size, depending on the application.

The most appropriate sample rate and bit depth for a digital audio project depend on the intended use of the audio. Here are some standard settings for various applications:

  • CD Quality: Sample Rate: 44.1 kHz Bit Depth: 16-bit

    This is the standard for audio CDs and is often used for consumer audio distribution. It’s more than adequate for most music listening situations since it covers the full range of human hearing.

  • DVD, Blu-ray, and Video Production: Sample Rate: 48 kHz Bit Depth: 16-bit or 24-bit

    48 kHz is the standard for most video formats, including DVD and Blu-ray. A bit depth of 24-bit is often used in video production to give more headroom for audio edits and processing.

  • Professional Music Production: Sample Rate: 44.1 kHz, 48 kHz, 88.2 kHz, or 96 kHz Bit Depth: 24-bit

    Higher sample rates like 88.2 kHz or 96 kHz may be used for professional music recording and mixing to capture more detail and allow for high-quality processing. However, the final product is often downsampled to 44.1 kHz for CD or digital distribution. The 24-bit depth provides more dynamic range, which is ideal for recording and editing.

  • High-Resolution Audio: Sample Rate: 96 kHz or 192 kHz Bit Depth: 24-bit

    For audiophiles and certain types of professional audio work where the highest possible audio quality is desired, high-resolution audio settings are used. Keep in mind that these settings result in very large file sizes and the differences may not be perceptible to the average listener on typical playback equipment.

  • Voice Recording (Podcasts, Audiobooks, etc.): Sample Rate: 44.1 kHz or 48 kHz Bit Depth: 16-bit or 24-bit

    For spoken word, a sample rate of 44.1 kHz or 48 kHz is more than sufficient. A bit depth of 24-bit is great for recording to avoid clipping and to allow for volume adjustments in post-production.

  • Streaming: Sample Rate: 44.1 kHz or 48 kHz Bit Depth: 16-bit

    For streaming services, 44.1 kHz or 48 kHz at 16-bit is the standard. Most streaming platforms will encode uploaded audio to their own specifications, often using lossy compression formats like AAC or MP3.

In general, it’s reasonable to record in the highest quality you can manage (considering your equipment and storage space), especially if you plan to process the audio. However, for distribution, you should consider the standards of the medium (like CD or streaming services) and the capabilities of the typical listener’s playback equipment.

Types of Audio Formats #

  • Uncompressed Formats
    • WAV Standard for Windows systems.
    • AIFF Standard for Apple systems.
  • Lossless Compression Formats
    • FLAC Free Lossless Audio Codec, maintains high quality. open-source
    • ALAC Apple’s version of a lossless codec.
  • Lossy Compression Formats
    • MP3 Most commonly used, but with some quality loss.
    • AAC Advanced Audio Codec, used primarily by Apple.
    • OGG Open-source and royalty-free, used in some games and systems.

Characteristics to Consider #

  1. Bit Rate: The amount of audio data processed per unit of time, measured in kbps.
  2. Sample Rate: The frequency at which audio signals are captured or played back, measured in Hz.
  3. Channels: Mono, Stereo, or Multi-channel audio.
  4. Metadata: Information like artist, title, and album that can be embedded in the audio file.

Applications and Use-Cases #

  1. Research: Uncompressed or lossless formats for maximum data integrity.
  2. Music Production: High-quality formats like WAV or FLAC for production, MP3 or AAC for distribution.
  3. Podcasting: MP3 with a moderate bit rate for a balance between quality and file size.
  4. Streaming: Adaptive bit rate formats like AAC for smoother online playback.