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Knowledge document #97

Poor voice quality when conducting calls

When conducting calls, one of the following issues either occasionally occurs or always occurs:

  • When conducting calls, you experience disturbances such as echo, dropouts, delays or background noise.
  • A loud and annoying hiss is heard when conducting calls. 
  • The voice of one or both parties sounds distorted or "choppy".

Note:All instructions on configuration and settings given in this guide refer to the latest FRITZ!OS for the FRITZ!Box.

Simply proceed as described below. After each measure, check whether the problem is solved.

1 Installing the latest FRITZ!OS for the FRITZ!Box

  1. Install the latest FRITZ!OS on the FRITZ!Box.

2 Installing the latest software for your telephone

The following steps are only necessary if you are using a FRITZ!Fon:

  1. Install the latest software on the telephone.

3 Disabling noise suppression on your analog landline

Noise suppression for analog landlines was implemented in the FRITZ!Box with FRITZ!OS 6.0. When noise suppression is enabled, under some circumstances this can result in deterioration in the voice quality and/or volume fluctuations when conducting calls from the analog landline. Therefore, disable this in the FRITZ!Box for testing purposes:

  1. Enter #614*1*#91** on your telephone and press the call key (pick up the handset).
  2. Hang up again after about 3 seconds.

    Note:You can reactivate noise suppression by entering #614*0*#91**.

4 Excluding repeater(s) as a cause of error

The following steps are only necessary if you use one or more repeaters to increase the DECT range of the FRITZ!Box and you hear the background noise when making calls with cordless telephones:

  1. Unplug all of the repeaters.
  2. Check whether you still hear background noise when you use a cordless telephone to make a call near the FRITZ!Box.
  3. If you no longer hear background noise, follow the steps in our guide Background noise when using a DECT repeater. In this case, the repeater is either not correctly connected with the FRITZ!Box or it was not positioned correctly.
    • If you can still hear background noise, plug the repeater in again and continue with the next section.

5 Disabling HD telephony on your ISDN line

The following steps are only necessary if you are using the FRITZ!Box on an ISDN line and you cannot understand the other party when they speak (very distorted, extremely noisy, robotic voice, or static and crackling can be heard).

  1. Enter #962*2* on your telephone and press the call key (pick up the handset).
  2. Hang up again after about 3 seconds.

    Note:You can re-enable HD telephony by entering #962*1*.

6 Restarting the FRITZ!Box

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Backup" in the "System" menu.
  3. Click on the "Restart" tab.
  4. Click the "Restart" button.

7 Checking the DSL connection for errors

A bad DSL connection has the greatest impact on applications that require real-time transmission, such as internet telephony. It especially affects upload, thus affecting the quality of voice data being transmitted to the party being called. Therefore, check whether the quality of the DSL connection is sufficient for conducting internet calls:

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "DSL Information" in the "Internet" menu.
  3. Click on the "DSL" tab.
  4. Check in the section "Error Counter" whether "Not Remediable Errors" (CRC) occur in the FRITZ!Box or the DSL exchange while you conduct a call over the internet.
  5. If no errors occur, continue with the next section. The signal quality is sufficient for conducting internet calls.

8 Reducing the call volume on the telephone

  1. Reduce the call volume on the telephone.

    Note:If you want to reduce the call volume on your FRITZ!Fon, press the "down arrow" or "telephone book" icon on the control ring while speaking on the telephone.

9 Registering cordless telephones with the FRITZ!Box

  1. Register all cordless telephones with the base station of the FRITZ!Box and switch off any other base stations.

10 Restoring the telephone to its factory settings and re-registering it

The following steps are only necessary if only a FRITZ!Fon is affected and other telephones do not have problems with voice quality:

Restoring the telephone to its factory settings

  1. Press the "Menu" key on the telephone.
  2. Scroll to "Settings" and press "OK".
  3. "Reset" > "OK" > "OK"

Deleting the telephone

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephony Devices" in the "Telephony" menu.
  3. Click the (Delete) button to delete the respective telephone.

Restarting the FRITZ!Box

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Backup" in the "System" menu.
  3. Click on the "Restart" tab.
  4. Click the "Restart" button.

Re-registering the telephone

  1. Register the telephone with the FRITZ!Box.

11 Configuring the FRITZ!Box for internet telephony

The following steps are only necessary if you use the FRITZ!Box to conduct calls over the internet (VoIP):

Setting the speed of the line

The following step is only necessary if the FRITZ!Box is not connected directly to a DSL line:

Note:When used as a DSL router (standard), the FRITZ!Box determines these values automatically.

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Account Information" in the "Internet" menu.
  3. Click "Change connection settings".
  4. Enter the speeds of your internet connection in the "Upstream" and "Downstream" fields in the section "Connection Settings".

    Example:
    Enter 2000 for an upstream of 2 Mbit/s; enter 32000 for a downstream of 32 Mbit/s.

  5. Click "Apply" to save the settings.

Setting up a prioritization rule for internet telephony

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Filter" in the "Internet" menu.
  3. Click on the "Prioritization" tab.
  4. Check if there is a rule for "Internet telephony" under "Real-Time Applications".
  5. If there is no rule, click "New Rule".
  6. Select "All devices" (default) as the network device from the drop-down list.
  7. Select "Internet telephony" from the drop-down list "Enter the network application:".
  8. Click "OK" to save the settings.

Configuring other applications

Applications such as file sharing software and online games establish many simultaneous internet connections. Although the "Traffic Shaping" function of the FRITZ!Box ensures that voice data is prioritized and evenly transmitted, for technical reasons it can only compensate for disturbances caused by these applications to a limited extent. This is why many applications offer the following setting options:

  1. Decrease the number of simultaneous connections allowed by the application.
  2. Reduce the maximum throughput available in the application..
  3. If you still experience problems or the application does not offer these settings options, configure the application as a background application in the FRITZ!Box.

The FRITZ!Box's echo compensation and traffic shaping functions guarantee high voice quality. However, if you still experience an echo, delays or short dropouts, they are caused by the telephone, your internet service provider or telephony provider, and cannot be influenced by the FRITZ!Box.

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