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Audio Loudness Monitoring How-To Guide


What is Loudness?

Overall loudness of a program needs to be maintained within the listening environment. If there are significant variations between programs or between channels, the user will invariably have to reach for the remote control to change the volume to a suitable listening level. This can lead to user frustration as they have to constantly change the volume control between programs and between channels. The broadcast chain needs to maintain a suitable average loudness for the various programs they are transmitting.

Loudness is a subjective measurement and is primarily a psychological correlation with the physical intensity of the audio signal. Different people will perceive the loudness of the signal differently and therefore a variety of techniques have been used to characterize the overall loudness of the signal. The ITU-R BS.1770 standard (algorithms to measure audio program loudness and true-peak audio levels) is one method for measuring loudness within broadcast environments. The ITU-R BS 1770 standard has been adopted by ATSC within recommend practice A85 Techniques for Establishing and Maintaining Audio Loudness for Digital Television and EBU recommendation R128 Loudness normalisation and permitted maximum level of audio signals.

How to Configure the Audio Loudness Monitoring

  1. Select one of the tiles (1,2,3,4) and press the Audio button
  2. Select FULL to make the display full screen, pressing FULL again will toggle back to FlexVu.
    On WFM/WVR5200 series use the Thumbnail button to cycle through the tiles and push and hold the Thumbnail button to toggle between Full and four tile modes.
  3. Press and hold the Audio button to display the menu.
  4. Move up and down the menu using the Arrow Keys or General Knob to the Loudness Meter menu.
  5. Enter the sub menu by pressing SEL and navigate to the Program selection. (Figure 1)
Audio Display with Audio Loudness Meter
Figure 1. Audio Display with Audio Loudness Meter.

Note:- The Audio Loudness meter is available for Analog, AES, Embedded and Dolby inputs depending on options installed within the instrument. The Loudness meter is not available in Embedded 16-Ch mode.

How to Quickly Configure the Loudness Measurements Presets for ATSC or EBU Standards.

Within the Config menu of the instrument there are a variety of settings for the Loudness measurements within the Loudness Settings menu.

To simplify the operation of the instrument Loudness Presets are available to quickly configure the unit to the appropriate standard recommendations.

  1. Press the Config button to enter the configuration menu.
  2. Move up and down the menu using the Arrow Keys or General Knob to the Loudness Settings menu
  3. Press SEL to enter the sub menu and navigate to the Loudness Preset menu.
  4. Depending on the user requirements you can select ATSC A/85, EBU R128 (+9 scale), EBU R128 (+18 scale), IEC61672 or ARIB TR-B.32. Navigate to the appropriate selection and press SEL to enable this preset.
Loudness Preset Configuration menu
Figure 2. Loudness Preset Configuration menu.

Note:- When the Loudness preset is selected within the Loudness Settings menu. Settings that are changed within the Loudness Settings menu by the loading of the Loudness preset will be shown in yellow text. Information regarding the settings of the Loudness presets can be obtained by pressing the HELP button on the front of the instrument.

Elements of Audio Display with Loudness Measurements.

Audio Tile Display
Figure 3. Audio Tile Display.
  1. Loudness Meter is enabled from within the Audio Tile menu and can be selected to show the Loudness for the program, a channel pair or disabled and not displayed within the audio tile. The Program Loudness (PL) is a summation of a number of audio channels. The channels that are included in the summation are indicated within the audio display by green channel labels. The channels that are not included in the program loudness and are indicated by white channel labels.

    The Loudness meter scale is configured by the user within the Config menu of the Loudness Settings.
    Target Loudness is indicated by the White Diamond shape at the side of the meter. Yellow and Blue Diamond shapes indicates the allowed high and low user defined loudness thresholds.
    Too Loud threshold is indicated by the Red Diamond shape.
    Too Quiet threshold is indicated by the Grey Diamond shape.
  2. Short Duration – Applies the variable time duration to the integration window of the loudness measurement. The Average Integration Time defines the duration of the integration window and is configured within the Loudness Settings menu. The value can range from 1 to 60 seconds.
  3. Infinite Duration - Integrates the loudness measurement continuously over the audio session duration. The audio session can be started, stopped or reset by the user. If gating is applied then some measurement results may be excluded from the loudness measurements.
  4. Dialnorm – An AC-3 metadata parameter, numerically equal to the absolute value of the Dialog Level, carried in the AC-3 bit stream. Valid values are 1 – 31. The value of 0 is reserved. The values of 1 to 31 are interpreted as –1 to –31. This display shows the current metadata value decode from the Dolby stream or from the SMPTE 2020 ancillary data packet.
  5. True Peak – Shows the current maximum True peak value and indicates the channel that has recorded the maximum true peak level. The audio level is four times oversampled per ITU-R BS 1771 for each audio channel and shows actual signal peaks regardless of their duration. An in-bar peak indicator will persist at the peak level for the "Peak Hold Time". For the ATSC standard a maximum True Peak value of -2dBFS is allowed and the EBU recommends a value of -1dBFS.
  6. Audio Session Duration – The duration of the audio session is show in time and indicates how long the audio session has been running since the last reset. The session can be started and stop using the Up or Down arrows and can be reset by using the SEL button within the audio tile.
  7. Audio Channel Labels – The audio channel labels can be numbered in channel pairs (1,2,3…) or can be configured to show the surround channel labels (L, C, R, Ls, Rs, Lfe..). The audio program config within the audio input/outputs configuration menu defines the audio mappings ( 8x1 (Mono), 4x2 (Stereo), 2x3 (LCRS), 2x2 2 (Quad), 2x3.1 (LCRLfe), 5.1 + 2 (Surr + Stereo), 7.1, 2 + 5.1 (Stereo + Surr). These audio program configuration define the number of programs present within the audio bars and how to sum the audio channels within the program. The audio channel labels below the audio bars indicate whether this channel is included within the audio Loudness summation. A Green channel label indicates that the audio channel is included in the Loudness summation. Whereas a White channel label indicates that the audio channel is not included in the Loudness summation. The summation of the number of channels can be configured by the user within the Loudness Settings menu.
  8. Audio Program number - Specifies the audio program currently being used for the program loudness. Within the Config menu the audio program can be configured by the user for AES or Embedded inputs and configured automatically for Dolby streams based on metadata. For instance stereo would use a Audio Program Config of 4x2 (Stereo) providing 4 different stereo program (1-4) for the 8 audio bars.
  9. Audio Ballistic - Specifies the response characteristics of the level meters. Choices are True Peak, PPM (Peak Program Meter) Type 1, PPM Type 2, VU, and Loudness.
  10. Loudness Ballistic - Specifies the response characteristics of the Loudness meters. Choices are Short Average, Long Average, Ungated Long, IEC 61672 F, IEC 61672 S and EBU R128 M (Momentary).

How to Configure Loudness Readouts within Audio Display

A user may specifically be interested in the Loudness measurements made by the instruments and to be able to quickly read the values within the audio display. To configure this display as shown in Figure 4 perform the following operations.

  1. Select one of the tiles (1,2,3,4) and press the Audio button
  2. Select FULL to make the display full screen, pressing FULL again will toggle back to FlexVu.
    On WFM/WVR5200 series use the Thumbnail button to cycle through the tiles and push and hold the Thumbnail button to toggle between Full and four tile modes.
  3. Press and hold the Audio button to display the menu.
  4. Move up and down the menu using the Arrow Keys or General Knob to the Aux Display menu.
  5. Enter the sub menu by pressing SEL and navigate to the Loudness selection (Figure 4)
Loudness Readouts within Audio Display
Figure 4. Loudness Readouts within Audio Display.

Figure 4 provides large number readouts for the Short Loudness Duration and Infinite Loudness measurement, along with values for maximum True Peak and Loudness Range measurement, based on the statistical distribution of loudness as defined within EBU R128 and EBU Tech 3342. Loudness Range which is defined within EBU R128 and quantifies the variation of the loudness measurement. The Loudness Range measurement is based on the statistical distribution of loudness within a program.

Audio Session Display

How to Configure the Audio Session Display

  1. Select one of the tiles (1,2,3,4) and press the Status button
  2. Select FULL to make the display full screen, pressing FULL again will toggle back to FlexVu.
    On WFM/WVR5200 series use the Thumbnail button to cycle through the tiles and push and hold the Thumbnail button to toggle between Full and four tile modes.
  3. Press and hold the Status button to display the menu.
  4. Move up and down the menu using the Arrow Keys or General Knob to the Display Type menu.
  5. Enter the sub menu by pressing SEL and navigate to the Audio Session selection. (Figure 5)
Audio Session Display
Figure 5. Audio Session Display

The audio session display contains a variety of summary information on each channel of the audio signal for the number of clips, mute, over and silence events that have occurred during the audio session Run Time. Additionally the maximum Peak and High audio level for each channel are also displayed.

Note:- The Peak value in the audio session display is the True Peak audio level measurement and the High audio level value is based on the ballistic used for the audio level. The True Peak measurement is based on a four times oversampling of the audio signal as specified in ITU-R BS.1771.

For audio loudness measurements a calculation for each channel and channel pairs is shown in the audio session display, along with the Program Loudness for the short and infinite duration. The Program Loudness measurement is based on a summation of a number of the audio channels and the duration of the measurement. The information on the number of channels summed together is provided within the Chans: display and the Short PD: label indicates the duration of the short period used for the Short term Loudness measurement. The infinite duration of the Loudness measurement is based on the Run Time of the audio session and can be stopped, started or reset by the user.

Note:- To stop or start the audio session press the up or down arrows in either the audio tile or audio session display. Press SEL to reset the Run Time of the audio session in either the audio or audio session display.

Loudness Session

The ALOG option is required for the WFM7x20 and WVR7x20 Series in order to display the Loudness Session that shows a trend chart of the loudness measurements and the ability to save the data to USB or download to a PC via a network connection.

How to Configure the Loudness Session Display

  1. Select one of the tiles (1,2,3,4) and press the Status button
  2. Select FULL to make the display full screen, pressing FULL again will toggle back to FlexVu.
    On WFM/WVR5200 series use the Thumbnail button to cycle through the tiles and push and hold the Thumbnail button to toggle between Full and four tile modes.
  3. Press and hold the Status button to display the menu.
  4. Move up and down the menu using the Arrow Keys or General Knob to the Display Type menu.
  5. Enter the sub menu by pressing SEL and navigate to the Audio Session selection. (Figure 6)

There are two types of charts available within the instrument. A trend chart (Figure 6) that shows a graph of the loudness measurements for the last 90 or 180 seconds and a bar chart that shows the maximum and minimum loudness value during each bar period and can show the loudness variations from 7.5 minutes to 30 hours instrument (Figure 7).

Loudness Session – Trend Chart 90 Seconds
Figure 6. Loudness Session – Trend Chart 90 Seconds.

Configuration of Loudness Session Display.

With the Loudness Session display selected as the active tile (Bright Blue border around tile). Push and hold the Status button to display the Loudness Session menu.

The following selections are available within this menu.

  • Mute Alarms Alarm reporting can be temporarily muted.
  • Graph Scale The horizontal scale of the chart can be changed from 0-90 and 180 seconds trend chart to 7.5 minute to a 30 hour bar chart.
  • Graph Gain The vertical gain of the chart can be changed between 0-60, 8-40 and 12-36dB.
  • Save History to USB Allows downloading of all loudness session data to a memory stick inserted into the front of the waveform monitor. Alternatively the loudness session log can also be downloaded via a network connection to the instrument.
  • History Reset Resets the Audio Loudness Session history.
  • All Sessions Reset Resets all audio and video sessions.

Resetting Audio Loudness Session Chart

The statistics on the Audio Loudness Session chart continue to accumulate until you manually restart the data collection or cycle the power.

With the Loudness Session displayed and selected as the active tile (Bright Blue border around tile). Press and hold the STATUS button to display the STATUS pop-up menu. Scroll to History Reset and press SEL to reset the session.

Loudness Session Bar Chart six hour duration
Figure 7. Loudness Session Bar Chart six hour duration.

Elements of Loudness Session Display.

  1. Loudness History: Shows a graphical display of Loudness measurements over time. A trend chart is available for durations of 90 or 180 seconds and a bar chart from 7.5 minutes to 30 hours on the instruments.
  2. Scale: Indicates the time interval over which the loudness measurements are made. This can be configured within the Loudness Session menu. When a Bar chart is selected the top left of the chart shows the duration of each bar and an update icon shows when the next bar will be added to the chart (Figure 7).
  3. LKFS short Loudness measurement based on duration of short period.
  4. LKFS inf. Infinite Loudness measurement based on duration of audio session.
  5. Dialnorm is the metadata value that is present either within the Dolby data stream or carried as an Ancillary data packet per SMPTE2020.
  6. True Peak is the maximum true peak value recorded by the audio meters. More detailed information on the true peak level of each channel is displayed within the audio session.
  7. Max Value The maximum Loudness value recorded within the loudness session.
  8. Min Value The minimum Loudness value recorded within the loudness session.
  9. Loudness Session Avg. The Loudness session average that is a summed average of all the values recorded in the session.
  10. Channel Summation Shows the summation of audio channels currently used to compute the Loudness average.
  11. Short Period Displays the current duration of the short period Loudness average.
  12. Target Value Displays the current user defined Target Loudness level.
  13. Loudness Session Time Displays the current duration of the Loudness Session since last reset.

Saving the Loudness Measurements Session Data.

If you are using an 8000, 5200 or WFM7x20 Series waveform monitor then you can save the Loudness measurement data to a USB stick in the following way (for a WVR7000 or 6000 Series the Loudness session data can be stored via the network):

  1. Insert a memory stick into the front of the waveform monitor. You may have to wait a moment for the memory stick to be mounted within the instrument. To check the status of the USB device press the MAIN button and verify that the USB stick is mounted. If the USB stick is mounted then the menu will show USB Unmount that indicates the next action will unmounts the drive. If the USB device is not installed and indicates USB Mount then press SEL to mount the device or check the status of the drive.
    You may have to try a different device if the USB stick is not recognized by the unit.
  2. Select the Loudness Session as the active tile (Bright Blue border around tile). Press and hold the STATUS button to display the STATUS pop-up menu.
  3. Navigate to Save History to USB using the arrow keys or general knob.
  4. Press SEL to automatically save the Loudness session data to the USB memory device. A progress bar will be shown in the status menu to indicate the transfer of the file.
  5. The Loudness Session data will be automatically stored in a folder using the Instrument name InstrumentName LoudnessHist. Within this folder a file will be created of the Loudness History using the Instrument Name, Date and Time of the instrument as the file name.
  6. Once the data is saved to the memory stick please remember to Unmount the device which can be done under the Main button menu. In order to prevent loss of data on the USB device.

You can also download the Loudness Session data use a PC and a network connection to the instrument.

  1. Connect the instrument to a PC through an ethernet hub or a direct connection with a crossover cable to back of the instrument.
  2. To allow network access to the instrument, you need to set the IP address. Network addresses can be assigned either automatically (DHCP) or manually. If your network does not use DHCP, you will have to manually enter the address for the instrument. Your LAN administrator will be required to provide a manual fixed IP address for you to use on a company network.
  3. Press the CONFIG button to display the configuration menu and navigate to Network Settings. Press SEL to enter the submenu.
  4. Navigate to Web Enable using the arrow keys or general knob and ensure On is selected.
  5. Set the IP Config Mode to Manual or DHCP depending on your network setup. If using DHCP you can skip steps six and seven.
  6. Select IP Address if entering an address manually and then use the dialog box to enter the values required using the arrow keys to navigate and SEL to set between each value.
  7. Similarly select Subnet Mask and Gateway Address with the appropriate network parameters provided by your LAN Administrator.
  8. Once the network is setup open a Web browser application on the PC (such as Internet Explorer or Firefox) and enter the IP address within the dialog box.
  9. If the connection is established between the PC and instrument a Tektronix Remote Interface web page should be displayed.
  10. Select View Loudness History (text, html) from this web page (Figure 8). Depending on your network connection speed and the length of the Loudness History this download process can take several minutes.
  11. The file can be saved to your PC using the web browser application.
Tektronix Remote Interface
Figure 8. Tektronix Remote Interface.

Once the data has been downloaded to the PC the html file can be imported directly into a spreadsheet application. Using the spreadsheet application the data can be manipulated in a variety of ways and charts can be produced from the data.