The sound source often consists of multiple distinct parts, and each microphone has its unique sound capture range. Can different types of microphones be used to accurately record these diverse sound sources? This is a key issue that audio professionals cannot overlook.
Nowadays, there are numerous microphone types available, with the most common being dynamic moving-coil, condenser, gooseneck, head-worn, and lapel microphones. Each type has its own pickup characteristics and is suited for different recording scenarios.
For vocal recordings, dynamic microphones and condenser microphones are frequently used in radio studios. Dynamic mics are robust and durable with high sensitivity and excellent directionality, producing clear, pure, and soft sounds with a frequency response ranging from 40 Hz to 16 kHz. Condenser microphones offer superior sound quality and sensitivity, delivering full, bright, and nuanced audio with a frequency response covering the human audible range of 20 Hz to 18 kHz. They also possess excellent directional properties, such as the Neumann U89i model, which offers five pickup patterns: omnidirectional, hemispherical, cardioid, supercardioid, and figure-eight. This versatility allows them to adapt to various recording conditions.
In radio broadcasting, where clarity and resolution are crucial, cardioid or supercardioid dynamic or condenser microphones are typically employed. Cardioid microphones have unidirectional pickup, capturing only the sound in front of them. Ideally, the speaker’s mouth should align with the microphone's central axis at a 0° angle for optimal output. If the speaker moves significantly while speaking, causing the mouth to deviate from the microphone’s axis, the sound energy may weaken or distort. Figure-eight directional microphones, on the other hand, are bidirectional, picking up sound from both the front and back, making them suitable for interview setups.
Omnidirectional microphones can capture sound in all directions, offering a 360° pickup area. The Neumann U89i, for instance, provides a broad pickup zone, ideal for large-scale recordings.
When recording radio programs, it’s essential to understand the directional characteristics of the microphone and adjust the distance between the microphone and the sound source. The pickup distance impacts the sound quality, affecting the proportion of direct sound to reverberant sound. The "direct-to-reverb ratio" influences the clarity of the sound. If the microphone is too close to the sound source, the low frequencies may overpower, resulting in a lack of layering and spatial depth. Conversely, if the microphone is too far away, the vocal clarity suffers, the sound becomes faint, and the intelligibility decreases. Practical experience shows that under ideal indoor acoustics with balanced frequency responses and even sound power distribution, the microphone’s pitch angle, height, and distance from the sound source should be finely adjusted to ensure the best pickup angle and effective distance, guaranteeing both clarity and coherence of the sound.
Despite these considerations, several factors can still impact the clarity of speech, such as plosive sounds in vocals. Microphone popping occurs when the diaphragm vibrates due to air pressure, leading to clicks when the voice is too loud. To mitigate this, one can increase the pickup distance slightly, adjust the microphone's angle to avoid the direct airflow, or activate the microphone's pad switch to reduce distortion, lower the gain, and enhance sound quality. Another common issue is inconsistent vocal volume, which can vary based on the angle, orientation, and distance of the microphone or inconsistencies in the sound source's quality, characteristics, and frequency. In real-world recording operations, adjusting audio frequency bands using a mixer and peripherals is critical for achieving audio balance. Broadcast studios or newsrooms often employ hardware peripherals like equalizers, compressors, effects processors, and frequency shifters to enhance vocal tone and ensure clear language programs.
Television audio pickup shares similar principles with broadcasting but demands higher sensitivity and directivity from the microphones. Most cameras today are equipped with dual microphones: one mounted above the body, following the camera’s axis to point toward the sound source, and another capturing ambient sound around the camera. These microphones usually have supercardioid pickup patterns, ensuring that the captured sounds align with the camera's projection direction.
With advancements in microphone technology, various designs have been created to suit different environments, including handheld, clip-on (lapel), and gooseneck microphones. Recently, microphones have become increasingly discreet, with gooseneck arms shortening. For instance, during CCTV news broadcasts, viewers rarely notice the pickup microphones, avoiding visual interference with the host’s face. Gooseneck and shotgun microphones are widely used in conferences due to their high sensitivity and directionality, effectively capturing speakers’ voices while suppressing background noise and feedback. They are ideal for live events, video conferencing, interviews, and TV broadcasts.
Musical instruments are vital sound elements in performances, with complex sound sources comprising strings, membranes, springs, rods, and air columns. A piano, for example, produces a wide range of sounds—crisp highs, rich mids, and deep basses. Two microphones can be used—one near the high strings and another near the bass strings. Placing a quasi-string microphone about 30 cm away captures a clear and full sound. Violins produce beautiful, shiny tones when the bow rubs against the strings. An omnidirectional microphone positioned above the bridge can capture soft and elegant sounds. Cellos emit thick, resonant tones, akin to bass, and are best captured above the bridge. Woodwinds, vibrating air columns, benefit from a cardioid dynamic microphone placed near the tube opening about 40 cm away for a soft and bright sound. Brass instruments like trumpets, trombones, and horns project loud, bright tones from the bell. When using a microphone, aim slightly off-axis from the bell to collect sound from areas outside the 50 cm zone. Using a condenser microphone with a 10 dB attenuation can yield excellent results.
Live performances of large concerts require careful microphone placement. The Neumann SM69 microphone covers a wide area and can capture the sound field's reverberation in X/Y and ORTF configurations. Auxiliary microphones, such as U87 and U89, can be placed in the midst of string, woodwind, brass, and percussion groups. Brass and percussion instruments have wide dynamic ranges, and dynamic microphones can achieve optimal acoustic effects.
When using multiple microphones, the auxiliary microphones' volume should be smaller than the main microphone to avoid disrupting the overall sound field. Microphone settings must be precise, arranging singers and instruments thoughtfully in the ensemble’s pickup positions. Each microphone's height, angle, and distance must be carefully adjusted during rehearsals. The relationship between the microphone and the performers is also significant. If the singer accounts for 60% of the sound field, the instrumentalists should contribute 40%. Depending on the instruments’ characteristics and melody changes, the balance can also be adjusted to 50:50. During regular performances, once the microphone and line adjustments are complete, the vocal levels should naturally follow, and the band’s seating arrangement should create a coherent sound image.
In conclusion, mastering the art of recording requires meticulous attention to detail. High-tech equipment demands careful calibration, and regardless of the quality of the sound source, human factors remain paramount. Only through complementary resources, skillful handling, and leveraging each microphone’s strengths can we achieve harmonious, natural sound reproduction and recreate the pleasing resonance of live performances.
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