How to use headphones without harm?

How to use headphones without harm?
  CCTV's "Weekly Quality Report" has conducted a survey on the quality of headphones: 3826 college students in a certain university use headphones as high as 99.8%, and there are more than 1,000 people with noise-induced hearing loss, accounting for nearly 30%.
  We can also see on the streets often, many pedestrians walking, riding a car will wear headphones to listen to music and watch videos. Everyone uses it so extensively. Have you ever cared about your ears? Is the headset I have been using qualified?
  The Bureau of Quality and Technical Supervision conducted spot checks on the earphone products produced in Shanghai. A total of 40 batches of products were spot checked. The 5 batches were unqualified. The unqualified items were the difference in the frequency response of the two headsets. B / T 14471-2013 "General Specifications for Headphones" provides as follows:
 The frequency response curve of the two headphones of the stereo headset, and the difference between the average sound pressure levels of the respective octave bands (whose center frequency is in the range of 250 Hz to 8000 Hz) should not be greater than 3dB. The difference between the average sound pressure level of the frequency response curve of the two ears of the non-stereo headphones in the specified frequency band should not be greater than 3dB.
 The sensitivity value corresponding to the frequency is the frequency response, referred to as frequency response. In simple terms, the wider the frequency response range usually means the wider the sound range of the headphones, so many people look at the frequency response range parameter when they choose the headphones. We must know that the earphone frequency response width can reach 5Hz-40000Hz, and the human ear's hearing range is only 20Hz-20000Hz. In other words, if the earphone is higher than the frequency response range of the human ear, we will not hear the higher part. Although frequency response is one of the important performance indicators for selecting headphones, Youpainet believes that we can't judge the quality of a headset solely by the frequency response range.Also related to the performance of the headset are harmonic distortion and rated impedance. There are 40 products that are qualified for harmonic distortion and rated impedance.
1.The output of a device cannot fully reproduce its input, resulting in waveform distortion or increase or decrease in signal components. Harmonic distortion is a kind of waveform distortion, which is indicated in the headset specifications. The smaller the distortion, the better the sound quality.
 2.The larger the impedance, the smaller the effect of the sound source output, and the smaller the voltage that the headphones can approach the sound source. The closer the distance, the more realistic the sound source.
    The main direct harm to the ear is the volume!
  A survey report released by the European Union: If you use headphones more than 89 decibels per day and listen to music for 60 minutes, it may cause permanent hearing loss in 5 years
What is 89 dB? The business of normal communication between people is generally around 50 decibels, and the highway environment is 70 to 80 decibels. Above 60 decibels is a noisy range. Above 70 decibels will damage the hearing nerves. Above 90 decibels will cause hearing loss. 100-120 decibels will temporarily lose hearing.
 If you need to wear headphones for a long time, it is recommended to choose in-ear headphones. In-ear headphones have a small sound contact area and a large pressure on the inside of the cochlea; headphones have a large contact area and low pressure, which stimulates the cochlea ciliary cells relatively little and is safer.
 In-ear headphone heads should be kept clean and can be disinfected and wiped regularly. In the noisy areas such as subways and buses, we will involuntarily raise the volume of the device in order to hear the content clearly. Such an approach can harm the ears! So if you have this bad habit, you must change it!