Lenovo A7-40 Tablet - Manual (Page 7)

Important safety and handling information
6
Prevent hearing damage
Your device has a headphone connector. Always use the headphone connector
for headphones (also called a headset) or earphones.
CAUTION:
Excessive sound pressure from earphones and headphones can cause
hearing loss. Adjustment of the equalizer to maximum increases the
earphone and headphone output voltage and the sound pressure level.
Therefore, to protect your hearing, adjust the equalizer to an appropriate
level.
Excessive use of headphones or earphones for a long period of time at high
volume can be dangerous if the output of the headphone or earphone
connectors do not comply with specifications of EN 50332-2.
The headphone output connector of your device complies with EN 50332-2 Sub
clause 7. This specification limits the device's maximum wide band true RMS
output voltage to 150 mV. To help protect against hearing loss, ensure that the
headphones or earphones you use also comply with EN 50332-2 (Clause 7 limits)
for a wide band characteristic voltage of 75 mV. Using headphones that do not
comply with EN 50332-2 can be dangerous due to excessive sound pressure
levels.
If your device came with headphones or earphones in the package, as a set, the
combination of the headphones or earphones and the device already complies
with the specifications of EN 50332-1. If different headphones or earphones are
used, ensure that they comply with EN 50332-1 (Clause 6.5 Limitation Values).
Using headphones that do not comply with EN 50332-1 can be dangerous due
to excessive sound pressure levels.