Here are some very interesting Videos by w2aew on YouTube. Videos #157 and #163 are on building a Circuit Board, for Audio Leveling - Normalizing. To achieve Automatic Audio leveling. This is much like an audio "Compressor Limiter". Used in Pro Sound Applications, when Mixing Sound for Concerts, Meetings and Theater. This one is used for an Auto Scanning Radio Receiver. Check out the Related YouTube Videos and info links, too...

Don

#163: Automatic Volume Level Control circuit demonstration | scanner

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Video link...

https://youtu.be/pUii_pDQxg8

· 246 videos

56,915

11,684 views

Published on Jul 30, 2014 · 2 years ago

In a recent video (linked below), I presented a circuit that was designed to be used with a scanning receiver, whose function was to provide a constant audio output level from the receiver - thus eliminating the annoying variations in volume of the various received signals. The video can be found here:
https://www.youtube.com/watch?v=1h0FZ...
In today's video, the circuit is demonstrated by connecting it up to a scanner and listening to the affect it has on the audio level of different received signals. Note that the automatic audio gain in the camera's recording system will tend to make the results with this circuit seem less dramatic than they really are when listening to it live.

Ludvig, SM6XUN, was kind enough to design a PCB for this design, and has made it available on OSH Park for anyone to order. The project can be found here:
https://oshpark.com/shared_projects/0...
And here are the schematic and PCB placement files:
http://www.qsl.net/w2aew/youtube/audi...
http://www.qsl.net/w2aew/youtube/audi...

Category
- Science & Technology
License
- Standard YouTube License

#157: Circuit fun: Automatic audio leveling circuit | audio compressor | for scanning receiver

Embedding disabled by request

Video link...
https://www.youtube.com/watch?v=1h0FZJYXQ_w&list=UL

· 246 videos

56,915

18,781 views

Published on Jun 27, 2014 · 2 years ago

This video presents a simple automatic audio volume leveling circuit. The application that prompted this is a police/fire/emergency scanner. Often times, different services will have different volumes in the receiver - so adjusting for a comfortable listening level on one service/station will often lead to other services being too loud or too quiet. This circuit will automatically adjust the volume of each received signal based on the signal's peak amplitude. Similar circuits have been widely published, so there's really nothing new here - just a quick tutorial and demonstration of how this circuit works. An arrangement of capacitors and diodes are used to implement a peak detector to measure the input signal amplitude. The dynamic impedance of diodes is controlled/changed to adjust the signal level. The result is a leveling circuit that has a very wide input dynamic range with a near constant average output level.

Note that fellow amateur radio operator SM6XUN created a PCB for this project, which can be found at:
https://oshpark.com/shared_projects/g...
Here is the schematic for this board:
http://www.qsl.net/w2aew/youtube/audi...
Note that you'll probably want to increase C4 to about 2.2uF....
Do you want to hear what this sounds like on a scanner, check out this followup video:
https://www.youtube.com/watch?v=pUii_...

Category
- Science & Technology
License
- Standard YouTube License

Audio normalization

From Wikipedia, the free encyclopedia

Audio normalization is the application of a constant amount of gain to an audio recording to bring the average or peak amplitude to a target level (the norm). Because the same amount of gain is applied across the entire recording, the signal-to-noise ratio and relative dynamics are unchanged.

Normalization differs from dynamic range compression, which applies varying levels of gain over a recording to fit the level within a minimum and maximum range.

Normalization is one of the functions commonly provided by a digital audio workstation.

Peak normalization

One type of normalization is peak normalization, wherein the gain is changed to bring the highest PCM sample value or analog signal peak to a given level – usually 0 dBFS, the loudest level allowed in a digital system.^[1]

Since it only searches for the highest level, peak normalization alone does not account for the apparent loudness of the content. As such, peak normalization is generally used to change the volume in such a way to ensure optimal use of available dynamic range during the mastering stage of a digital recording. When combined with compression/limiting, however, peak normalization becomes a feature that can provide a loudness advantage over non-peak normalized material. This feature of digital recording systems, compression and limiting followed by peak normalization, enables contemporary trends in programme loudness.^[2]^[3]

Loudness normalization

Another type of normalization is based on a measure of loudness, wherein the gain is changed to bring the average amplitude to a target level. This average can be a simple measurement of average power, such as the RMS value, or it can be a measure of human-perceived loudness, such as that offered by ReplayGain, Sound Check and EBU R128.^[1]

Depending on the dynamic range of the content and the target level, loudness normalization can result in peaks that exceed the recording medium's limits. Software offering such normalization typically provides the option of using dynamic range compression to prevent clipping when this happens. In this situation, signal-to-noise ratio and relative dynamics are altered.