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Audio frequency (AF) or audible frequency is characterized as a periodic vibration whose frequency is audible to the average human. The SI unit of audio frequency is the hertz (Hz). It is the property of sound that most determines pitch. The generally accepted standard range of audible frequencies for humans is 20 to 20,000 Hz, although the range of frequencies individuals hear is greatly influenced by environmental factors.

Frequencies below 20 Hz are generally felt rather than heard, assuming the amplitude of the vibration is great enough. High frequencies are the first to be affected by hearing loss due to age or prolonged exposure to very loud noises

Under the IPX7 designation, the product will be able to withstand immersion in water up to 1 meter for up to 30 minutes. This means that a session in the shower, getting caught in the rain, or washing your hands will not cause damage, but prolonged exposure —such as swimming —would be harmful.

IPX7 is a common rating for small portable electronics that are designed for use outdoors, but are not considered "rugged." Many handheld GPS units, for example, carry IPX7 ratings.

Dual drivers earphones are a special kind of earphones, as obvious from the name, are operated by two sets of drivers. Each earpiece contains two separate speakers — one to handle the high and mid frequencies, and one to handle the bass. This separation creates a more rich and filled-out sound that makes any kind of music sound better.

Advanced filtering in dual drivers will better separate sound frequencies from each other and will give you a much smoother and more precise sound frequency from low-end to high-end. An extra driver added to each side will give you that extra added sound quality you desire because with dual drivers each driver can be solely assigned to a specific frequency range giving you the advantage of not having a limit of sound frequencies in your audio. You’ll also have a more rich clear spacious sound that’s created by the separation of the sound frequency and naturally enhances your sound quality.

Earphones with dual drivers have a crossover network circuitry built inside of them that splits the signal path of different frequencies so you won’t have to buy any unnecessary extra equipment to get the sound quality sound you desire. You’ll naturally get a better bass response and sound signature.

Radio-Frequency Identification (RFID) is the use of radio waves to read and capture information stored on a tag attached to an object. A tag can be read from up to several feet away and does not need to be within direct line-of-sight of the reader to be tracked. Red Lemon RF ID blocking in this bag designed to impede your cards' RFID signals, making them harder to read remotely and secure your card's or chip data.

The element inside a headphone that converts an electrical signal into sound is known as a driver unit. You could picture it as a tiny loud speaker in your headphone.

A driver unit is made of a magnet, voice coils and a diaphragm. One would wonder how to measure a driver: by its radius, circumference or diameter? The diameter is the stated spec which is usually measured in millimeters. A driver unit's size is useful to gauge the capabilities of producing sound.

It may seem that the bigger the driver unit is, the louder the sound it's capable of producing. That's not true though, because for every headphone design, be it micro sized earphones or huge headphones, while the size of the driver unit varies, the loudest volume at which you would hear them, stays the same. The quality of the driver unit is what makes a huge difference to the sound. The size of the driver unit for earphones falls in the range of 8mm to 15mm and 20mm to 50mm for headphones.

Ear bud style earphones have bigger driver units as compared to canalphones because of their ability to house bigger units. Same is the case with headphones, an over-ear headphone will have bigger drivers as compared to on-ears.

Sensitivity tells you how much volume you'll get from a speaker with a given amount of power. Not only can it affect your choice of speaker, but also your choice of stereo receiver/amplifier. Sensitivity is integral to Bluetooth speakers, soundbars, and subwoofers, even though those products may not list the specification.

Speaker sensitivity is self-explanatory once you understand how it's measured. Start by placing a measurement microphone or SPL (sound pressure level) meter exactly one meter away from the front of the speaker. Then connect an amplifier to the speaker and play a signal; you'll want to adjust the level so the amplifier delivers only one watt of power to the speaker. Now observe the results, measured in decibels (dB), on the microphone or SPL meter. That's the sensitivity of the speaker.

The higher the sensitivity rating of a speaker, the louder it will play with a certain amount of wattage. For example, some speakers have a sensitivity of around 81 dB or so. This means with one watt of power, they'll deliver just a moderate listening level. Want 84 dB? You'll need two watts – this is due to the fact that every additional 3 dB of volume requires double the power. Want to hit some nice and loud 102 dB peaks in your home theater system? You'll need 128 watts.

Sensitivity measurements of 88 dB are about average. Anything below 84 dB is considered rather poor sensitivity. The sensitivity of 92 dB or higher is very good and should be sought after.

The impedance specification is ignored by most headphone buyers, but it might be one of the most important. Not that anything catastrophic will occur with an impedance mismatch, but you might not get the best sound quality from a headphone with impedance that's too high or too low for your music player or home amplifier.

Most headphones with low impedance (less than 25 ohms, approximately) require little power to deliver high audio levels. For example, low impedance headphones will work well with equipment with weak amplification like portable music players, phones, and other portable devices.

Headphones with higher impedance (25 ohms and over, approximately) demand more power to deliver high audio levels. As a result, they are protected from damage caused by overloading. They can also be used with a wider range of audio equipment.

The Qualcomm CSR8635 QFN single-chip Bluetooth audio ROM device targets mid-range stereo speakers and headsets.

The Qualcomm CSR8640 chipset is a 2 Mic Stereo ROM solution designed to support our customers develop a range of highly differentiated home entertainment and wearable audio products - more easily, in less time and cost effectively.

The Qualcomm CSR8645 dual-mode ROM audio SoC is designed to offer extensive voice and music capabilities in a ROM-based package, including aptX and cVc, making it ideal for a variety of wireless audio products with support for voice and music. It is an ideal solution for a range of highly differentiated home entertainment and wearable audio products including stereo headphones, speakers, speakerphones, headsets and hands-free devices.

CSR8675 is a premium tier single-chip solution delivering high quality wireless audio performance and supporting the development of highly differentiated premium wireless audio products. Integrated support for aptX, aptX HD, Active Noise Cancellation and Qualcomm TrueWireless stereo.

Qualcomm® aptX™ audio enhances the wireless sound quality of many of the world’s finest smartphones, speakers, soundbars, headphones and tablets. With aptX, music lovers can enjoy wired quality sound - wirelessly.

aptX is a strong, recognized technology in the consumer electronics marketplace, supporting all major platforms including Android, Win10 for PCs and Smartphones, Mac OS, and BBM.

Passive noise cancelling headphones work to block out sound waves from the environment by the materials that they are made out of, whether rubber tips in an in-ear design or padding in an over-the-ear design. Very simply, it’s the amount of noise cancellation offered by the physical device, or how well the headset works as an earplug.

While a good design will provide strong passive cancellation before electronics are applied, passive cancellation is often limited to cancelling frequencies above 1 kHz. Even the best active electronics can’t compensate for poor acoustic design with minimal passive cancellation.

Active noise cancellation (ANC) is the process of using a microphone to monitor environmental noise and creating anti-noise that’s then mixed in with audio playback to cancel noise entering the user’s ear.

Active noise cancellation can be achieved with analog filters or digital filters, and is generally differentiated by architecture: feed-forward cancellation, feedback cancellation or hybrid cancellation. As mentioned, great active cancellation will significantly improve a headset with good passive cancellation, but can’t make up for poor design.