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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".

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

1 Installing the latest software for your telephone

  1. Install the latest software on the telephone.

2 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*.

3 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.

4 Reducing the call volume on the telephone

  1. Reduce the call volume on the telephone: Press the "down arrow" or "telephone book" icon on the control ring while speaking on the telephone.

5 Removing USB 3.0 devices from the FRITZ!Box

If you are using a FRITZ!Box with USB 3.0 support and a USB 3.0 device is connected to the FRITZ!Box, the USB device may be interfering with the DECT connection:

  1. For testing purposes, remove all of the USB 3.0 devices from the FRITZ!Box's USB ports.
  2. If the problem no longer occurs then, a USB device was interfering with the radio connection. Eliminate the interference caused by the USB device.

6 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.

7 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.

8 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. In the "Downstream" and "Upstream" fields in the section "Connection Settings", enter the speeds of the internet connection for receiving (download) and sending (upload) data in Mbit/s. If the fields are not displayed, the speeds of the internet connection are determined automatically. In this case you cannot adjust them.
  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 "Apply" 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 allow you to make these adjustments, 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 internet service provider or telephony provider and cannot be influenced by the FRITZ!Box.

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