Binaural Recording: What Is It & How Does It Work

What is Binaural Recording?

Binaural recording is a method of recording audio that uses two microphones to create a 3D stereo sound sensation for the listener. The word “binaural” literally means “using both ears.” It works by capturing the subtle differences in timing, frequency and volume between the sound reaching each ear, which is how humans naturally hear in the real world. This allows for incredible realism and immersion when listening back on headphones.

The history of binaural recording dates back to 1881 when French engineer Clément Ader invented the théâtrophone, the first binaural recording device. It consisted of an array of multiple telephone receiver units along a concert hall balcony linked back to listeners with two earpieces, allowing them to experience concerts live from their homes. However, binaural recording technology remained largely dormant for the next hundred years.

In contrast to traditional stereo recording, which uses spaced microphone pairs to capture sound, binaural recording aims to record sound exactly as human ears hear it. The difference in arrival time, intensity and spectral qualities between the sound reaching each ear are preserved. This allows for localization of sounds horizontally, vertically and with depth when played back. Sound sources seem to originate from specific points in space, fully surrounding the listener.

How Does Binaural Recording Work?

Binaural recording aims to reproduce the natural listening experience of human hearing using two microphones to capture sound separately for the left and right ears. The technique uses a dummy head with embedded microphones in the ear positions to record audio in a way that mimics how we hear sounds spatially in real life. The goal is to create a 3D stereo sound sensation when listening back to binaural recordings using headphones.

Specifically, binaural recording relies on two omni-directional microphones placed where our ear canals would be on a human head. The microphones capture the subtle acoustic differences that occur naturally as sound waves wrap around the head. This provides directional cues and creates a sense of space, depth and distance. Our brain interprets these acoustic differences between our two ears to localize sounds and determine their origin and movement. Binaural recording tries to accurately capture these differences so that playback simulates natural hearing and localization.

For the full effect of binaural audio, recordings must be listened to using headphones. This allows each ear to hear a different signal corresponding to what each microphone captured separately. The effect generally does not translate to loudspeakers.

In summary, binaural recording aims to produce immersive, three-dimensional audio by replicating how sounds reach our ears in the real world. The technique can create a strong sense of space and realism when listening on headphones.


Equipment Needed

To create a proper binaural recording, specialized equipment is required. The most important pieces are:

– Two high quality condenser microphones: The microphones capture the subtle sonic details needed for binaural audio. Small diaphragm condenser mics are commonly used for their accurate reproduction. Research indicates that the quality of the microphones is critical for high fidelity binaural recording.

– Dummy head prop or other microphone rig: The microphones must be placed at the exact position of a human’s ears to capture the proper stereo image. This is commonly achieved by mounting the mics on a dummy head model. However, specialized rigs like the Core Sound binaural mics can also position the mics accurately.

– Audio interface with multiple inputs: To capture the stereo channels independently, the microphones require an interface with at least two mic preamp inputs. The audio interface enables routing the signals into a DAW for mixing and editing.

Microphone Placement

Proper microphone placement is crucial for capturing realistic binaural audio. The microphones should be positioned where the listener’s ears would be. This allows the microphones to capture the subtle sonic cues that our ears use to locate sounds spatially (Binaural Recording Techniques – The Complete Guide).

Typically, the microphones are placed approximately 7 inches apart, matching the average distance between human ears. The microphones should point inwards, angled slightly towards each other so they converge at a point a few feet in front of the head. This inward angle helps create a lifelike stereo image when the audio is played back through headphones (How to Record Binaural Audio (Methods & Equipment)). Precise positioning is important for capturing subtle timing and intensity differences between the ears, creating a strong sense of space and realism.

Mixing Binaural Audio

Mixing binaural audio requires special techniques to avoid collapsing the stereo field and maintain separation between the left and right audio channels (Source). Some key considerations include:

– Avoiding hard panning beyond the width of the head. Sounds panned hard left or right can seem unnatural and exaggerated in a binaural mix.

– Using subtle volume automation and EQ to simulate distance and movement. This helps create a sense of space and dimension.

– Keeping reverb sends moderate to avoid smearing the stereo image. Too much reverb can make things sound washed out.

– Being careful with compression to avoid pulling elements too far forward or collapsing the image.

– Checking on headphones regularly to ensure elements are clearly separated left and right.

With practice, binaural mixing allows creating immersive audio environments that put the listener right in the middle of the soundscape.

Binaural Recording Techniques

There are a few key techniques used in binaural recording to capture a realistic 3D audio image:

Using a binaural dummy head with built-in microphones is a common method. The microphones are placed in the dummy head to mimic the human auditory system, with one microphone near each ear canal. High quality binaural dummy heads like the Neumann KU100 can capture intricate acoustic details and create a convincingly lifelike stereo image (source).

Binaural in-ear microphone techniques are also popular. Small omni or cardioid mics are placed just outside the ear canal to capture a similar stereo image. Some rigs combine an in-ear mic on one side and a standard mic on the other. The in-ear mic picks up the direct sound while the standard mic captures room ambience (source).

Capturing movement and panning effects during recording helps create a more immersive binaural experience. As the mic rig moves through space, the directional relationships and stereo imaging shift in real-time. Rotating from side to side captures dynamic left-right panning. Moving forward and backward simulates approaching and retreating sounds (source).

Challenges and Limitations

While binaural recording can produce incredibly immersive audio, the technique also comes with some challenges and limitations. One major drawback is the cost of equipment needed. High-quality binaural microphones designed to capture spatial audio can be expensive, with some models costing thousands of dollars (source). The positioning and placement of the microphones is also difficult to get right. The binaural mic setup needs to be positioned perfectly to capture sound from a human perspective, making placement tedious and requiring a lot of trial and error (source).

Another significant limitation is that binaural audio does not translate well to speaker playback. The immersive effect of binaural recording is designed for and best experienced through headphones. When played through speakers, the spatial positioning is lost and the sound will not be perceived as three-dimensional (source). This limits the applications for binaural audio to media designed primarily for headphone listening.

Uses of Binaural Recording

Binaural recording produces exceptional spatial listening experiences, making it useful for several audio applications:

ASMR videos – The 3D, immersive audio quality enables listeners to experience the intimate “tingles” and “whispers” associated with ASMR content.

VR audio – Binaural recordings integrated with VR visuals create highly immersive virtual environments, with sounds seemingly coming from all directions.

Music recordings – Musicians can use binaural techniques during recording, mixing, and mastering to achieve a lush, multi-dimensional sound.

Sound effects – Sound designers in film, TV, and gaming often capture binaural samples of environments and Foley effects for enhanced realism.

As Florian Grond notes, the creative possibilities of binaural audio continue to expand as the techniques become more accessible.

Listening to Binaural Audio

Binaural audio is meant to be listened to with headphones. Using headphones is essential to achieve the proper 3D immersive effect that binaural audio aims to create. Headphones allow each ear to hear the separate audio track recorded for it, without any crosstalk between the ears. This allows your brain to perceive sound sources as externalized and placed at different points within the soundscape, creating a very realistic 3D listening experience.

Listening to binaural audio through speakers does not produce the intended 3D spatial effect. The two audio tracks blend together when played over speakers, eliminating the perception of directionality and space. This results in an ordinary stereo listening experience. For binaural audio to work as intended, headphones must be used to deliver the separate tracks independently to each ear.

With headphones, binaural audio provides a highly immersive listening experience, surrounding the listener with sound sources placed at different points in space. This creates the illusion of being present in the middle of a 3D soundscape, with sounds coming at you from all directions. It provides a sense of space and realism that standard stereo audio cannot replicate. The effect can make listeners feel like they are actually present in the middle of the scene or location where the audio was recorded.

According to Audiosorcerer, “When listening to binaural audio, it’s essential to use headphones because they allow you to hear the 3D audio effect properly. Without headphones, you won’t get the full experience”. So for the most immersive and realistic 3D audio experience, headphones are a must when listening to binaural recordings.

The Future of Binaural

Binaural recording techniques continue to evolve and improve as the technology gains popularity. Here are some key areas of development to expect in the future of binaural audio:

Continued growth for VR and ASMR – As virtual reality expands, binaural audio will play an integral role in immersing users in VR environments. Binaural recordings are also popular for ASMR, with specialized mics and techniques being developed to optimize ASMR audio. The demand for binaural content will likely continue growing in these areas.

New binaural mic techniques – Innovations in miniature microphone design and placement will allow for more lifelike binaural recordings. Miniature mics placed directly in the ear canal capture the most natural sound, and wireless options avoid cabling issues. Expect more advanced binaural mics to be developed.

Accessibility improvements – Binaural audio has potential to assist those with visual impairments by providing very realistic spatial audio. As the tech evolves, binaural recordings may be used to convey spatial information in an accessible way. This could significantly improve spatial awareness for the visually impaired.

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